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This is the single most important distinction in our lineup, and it's where most mismatched expectations come from.

Pro Series is built to your combination. It's stall-adjustable, uses a one-piece billet front, and covers the higher stall range. If you want a specific flash number, or you expect to change the stall later as the combo evolves, this is the one.

HP Series is a factory-replacement-style unit. Strong, well built, and the right call for a lot of setups — but the stall is what it is. There's no adjustability, and there's a practical ceiling on how much flash you'll see out of one.

The rule of thumb we use internally: if you're chasing a specific number much past the ~3,000rpm range on a typical setup, you're in Pro Series territory. A stock-replacement or mild build is well served by HP Series.

One more thing worth knowing up front — an HP Series unit can't be re-stalled later. If there's any chance you'll want to move the stall after you've driven it, start with Pro Series.

We custom-spec every converter, so the recommendation is only as good as the information behind it. Here's what actually moves the needle:

• Camshaft specs — duration, lobe separation, the whole card if you have it. This is the first thing we ask for every time, and we genuinely can't spec without it.
• Power adder — naturally aspirated, turbo, supercharger, nitrous. Include the setup and target boost if you know it.
• Transmission — model and whether it's stock, built, or has a modified valve body.
• Rear gear ratio and tire height — these change the answer more than people expect.
• Vehicle weight — a 4,200lb truck and a 3,100lb car want different converters.
• How you use it — daily driver, street/strip, dedicated drag, towing, mud. Be honest here; it matters more than peak horsepower.
• Target stall, if you have one in mind.

The fastest way to get all of this in front of a builder is the spec form — it walks you through it in about five minutes and it goes straight to someone who builds these for a living.

We won't give you a number off a chart, because the honest answer is that stall selection is a systems problem, not a lookup.

The same converter can flash 3,200rpm in one car and 3,800rpm in another. Cam timing, gear ratio, tire height, vehicle weight, converter charge pressure, and whether there's boost involved all move it. That's why every unit we build gets spec'd to a specific combination.

What we can tell you generally:

• Bigger cam, more gear, lighter car all push the effective flash up.
• Heavier vehicle, taller tire, less gear pull it down.
• Forced induction typically adds several hundred rpm of flash over the naturally aspirated number for the same unit.
• A converter that's too tight hurts your launch and makes the car feel lazy. Too loose and you'll live at high rpm, make heat, and lose efficiency on the highway.

Give us the combination and we'll put a real recommendation behind it — including what to expect on the hit versus on the motor.

Forced induction changes the converter selection more than almost any other variable.

Expect more flash than the naturally aspirated number. The same unit that flashes ~3,500rpm on motor will commonly see closer to 4,000rpm once the power adder is doing its job. We spec around the boosted number, not the N/A one, so tell us what's on the car before we build.

Series selection tightens up. There are combinations — particularly certain late-model multi-speed applications — where we'd steer you to a Pro Series unit specifically because a factory-replacement-style converter isn't the right tool behind that kind of torque. We'd rather tell you that up front than warranty it later.

Clutch capacity matters. Boost is where multi-disk earns its keep. If you're planning WOT lockup with a power adder, a single-disk setup is usually the wrong place to be.

Because this is where the stakes get expensive, we don't hand out boosted recommendations without seeing the whole combination first.

A multi-disk setup is all about durability. It gives you the clutch capacity to use lockup under power — what most people mean by WOT lockup.

Go single-disk when the car is street-driven, moderate power, and lockup is doing what the factory intended: cruising efficiency and highway manners.

Go multi-disk when you're locking the converter and then asking it to hold real torque — powering through the 1/8th or the 1/4, a boosted combination, or anything where you're carrying lockup at wide-open throttle. Trying to do that on a single-disk is how clutches get cooked.

There's a second, less obvious factor: with a billet front, a single disk can run a larger clutch area than it otherwise could, which raises the ceiling on what a single-disk setup can hold. That's part of why our billet fronts matter beyond just strength.

We offer several diameters because diameter is a primary design variable, not a packaging afterthought.

Broadly: a smaller diameter converter will stall higher for a given design and is the usual path to serious flash numbers. A larger diameter converter tends to be more efficient and does more of its work lower in the rpm range — better for a heavy vehicle, towing, or a combination that lives at part throttle.

But diameter never acts alone. It works together with the impeller and stator combination, the clutch setup, and your driving habits to determine where the converter actually stalls and how efficiently it couples once it's there. Two converters of the same diameter can behave completely differently depending on what's inside them.

That's why we spec by combination rather than selling you a diameter off a shelf.

Bolt pattern is application-specific and it's the detail most worth confirming before an order goes into production, because it's not something that can be changed after the fact.

Common reference points you'll see on orders include stock GM patterns specified by bolt count and bolt circle diameter, and legacy patterns for older applications. Which one you need depends on:

• Your transmission and how it's configured
• Your engine and its crank flange
• Your flexplate — factory, or an aftermarket billet unit, which may have a different pattern than stock

We also carry billet flexplates for common LS / LSA / Gen-V LT applications, and the matching crank bolts. If you're ordering a converter for a swap or a built combination, it's worth sorting the flexplate at the same time so the whole stack is known-good.

Tell us the engine, transmission, and flexplate you're running and we'll confirm the correct pattern before anything gets built. Getting this wrong is expensive and entirely avoidable.

Billet refers to the starting material: a bar or block of semi-finished steel, produced by rolling an ingot or bloom, that a finished part is then machined out of.

In converter terms, a billet front means the front cover is machined from one solid piece — not a stamped cover with tabs, feet, or ring adapters welded onto it. Everything is cut from the same block, so there are no welded joints in the load path.

That's the whole distinction, and it's why the word gets used loosely by people selling parts that aren't actually billet.

A billet front is a one-piece front, so the visual test is straightforward: you will not see any welded tabs, feet, or ring adapters.

If a mounting pad or a pilot ring looks like it was attached rather than machined in place, it isn't billet. On a genuine billet cover, every feature is cut from the same block of material, which is exactly what makes it strong.

This is also part of why we put so many photographs of our converters on the site. It's much easier to show you the machining than to describe it.

Two reasons, in order of importance.

Strength. The number one job is preventing the front cover from flexing under high rpm and high horsepower. A flexing cover is the beginning of a lot of expensive problems — it changes clutch clamp behaviour, it works the joints, and on a welded-together front it concentrates stress exactly where you don't want it.

Clutch area. A billet front allows for a bigger clutch area in a single-disk configuration than you can otherwise achieve. It's the only way to get certain single-disk setups to hold what we ask them to hold.

Our fronts add a few things beyond just being billet: CAD-designed geometry for strength, better curves through the load path, and longer bolt engagement than a mass-produced front gives you. Not all billet fronts are equal, and that's where the difference shows up.

There are two different ways a late-model converter transmits power to the transmission input shaft: hydraulically and mechanically.

The hydraulic path is the converter doing what a converter does — the impeller drives fluid into the turbine, and the fluid transmits the torque. There's always some slip in that arrangement, which is what allows the car to sit still in gear and what gives you torque multiplication off the line.

Lockup is the mechanical path. A clutch inside the converter clamps, tying the engine directly to the input shaft with no fluid coupling in between. Slip goes to essentially zero, efficiency goes up, and heat generation drops. It's why your highway rpm settles and your trans temps behave once lockup engages.

How much torque you can put through that clutch — especially at wide-open throttle — is what determines whether you need a single-disk or a multi-disk setup.

Flash stall is the rpm the engine will flash to when the car is launched from rest at wide-open throttle.

It's worth separating this from brake stall, which is what the engine will pull against the brakes sitting still. Those are different numbers, and brake stall is usually the lower of the two. When we quote a stall range, we're generally talking about flash.

Flash can be hard to pin down if the car has traction issues — if the tires break loose, the converter never really loads and the number you see isn't representative. The best way to measure it is at the track, or with a datalog that captures engine rpm alongside input shaft speed so we can see what the converter is actually doing rather than what the tach suggests.

Shift drop is what your rpm falls back to when you change gears.

For example: if you shift at 6,500rpm on the 2-3 shift and the engine settles at 5,300rpm, that's a 1,200rpm shift drop.

It matters because it tells you whether the converter is keeping the engine in its powerband between gears. Too much drop and you're falling out of the power every time you shift. Converter selection, gear ratio, and shift points all interact here — which is another reason we ask about gearing when we spec a unit.

The long way, for anything without an input shaft speed sensor:

Slip % = [((RPM × Tire Height) ÷ (Rear End Ratio × Trans Ratio × MPH × 336)) − 1] × 100

Where tire height is in inches and MPH is actual road speed.

The short way, if you have a late-model transmission: compare engine rpm to input shaft speed directly. Most modern setups log both. If they're 1:1, the converter is fully locked. The gap between them is your slip, and you don't need the formula at all.

That second method is also how we diagnose most converter complaints, which is why the input shaft speed channel is the one we ask for every time.

Furnace brazing is the method used to solidify the internal fins of the turbine and impeller. We run an exothermic atmosphere brazing furnace, which gives a clean, consistent bond across the fin-to-shell joints without the contamination you'd get from a less controlled process.

Why it matters: the fins are what actually move the fluid. If they flex or separate under load, the converter's behaviour changes — and not in a way you can tune around. Brazing locks that geometry in place.

TIG welding is used on the outer assembly where a precise, high-integrity weld is required. It's slower than the alternatives and that's the point.

One detail that comes up occasionally: the brazing process doesn't necessarily seal every single blade orifice where the blades pass through the turbine shell stamping, and the holes machined into the turbine bearing plate and hub are there by design — they provide pressure balance inside the converter and keep the charge oil flow path as unrestricted as possible. Neither is a defect, and we haven't found any detrimental effect on converter efficiency from either.

Our part numbers are a build code, not a catalogue number. We custom-spec each converter, so we don't just sell "a 3200" — we sell what will be a 3200 in your setup, which might be a different combination than it would be in someone else's.

Reading a number like 07-12-05-1D, the segments identify the application and transmission, the series, the diameter, and the clutch configuration. The trailing suffix — the 1D, 2B, 5C, 2D part — identifies the impeller number and stator combination. That's the pair that most directly determines where the unit stalls.

So a decode looks something like: 6L80, Pro Series, 258mm, single-disk lockup, #1 impeller with a 19-vane 35° stator combination.

Why we won't publish a full decode chart: the same impeller and stator combination lands at meaningfully different rpm depending on vehicle weight, gearing, tire, cam, and power adder. A number that flashes ~3,200rpm in one car will be somewhere else entirely in a full-size truck. Publishing a chart would create more wrong answers than right ones.

The part number is stamped or written on the side of the converter. Send us that plus the serial number and we'll tell you exactly what you have and what it should do in your combination.

A converter doesn't technically add engine horsepower. What it does is let you use more of the power you already have.

The biggest factor is stall. A higher stall means you're at a higher rpm the instant you take off, which means you're launching in the part of the curve where the engine actually makes torque instead of trying to pull from down low.

The second factor is efficiency. A well-matched converter couples more efficiently once it's loaded, so less of the engine's output gets turned into heat in the fluid and more of it reaches the ground.

The third is that the right converter keeps the engine in its powerband between shifts, which shows up as less shift drop and better recovery through the gears.

All three depend on the converter being matched to the combination — which is why a mismatched high-stall unit can make a car slower and hotter, not faster.

We like to educate, and a picture saves a lot of typing.

We use a number of unique build techniques — custom CNC work, specific machining operations, our own furnace brazing process — and the differences between a well-built converter and an average one are mostly visible. Showing you the actual part is more honest than describing it, and it lets you compare what you're buying against what else is out there.

It also helps when you're trying to verify what you have. Being able to look at photos of a known-good unit makes it much easier to spot when something isn't what it was sold as.

Our installation tips page covers the process. Two points are worth repeating here because they cause the most expensive mistakes:

Seat the converter fully. A converter that isn't fully engaged into the pump before the transmission is bolted up will destroy the pump on startup. You should feel it drop through distinct stages of engagement, and it should rotate freely with the correct clearance to the flexplate before you torque anything. If you're not certain it's home, pull it and start again — this takes ten minutes and saves a transmission.

Prime it. Add fluid to the converter before installation and don't start the engine dry.

Beyond that: verify the bolt pattern and pilot match your flexplate before install day, torque the converter bolts to spec in a cross pattern, and check flexplate-to-converter clearance rather than assuming it.

If you're unsure about the bolt pattern for your application, send us the part number and what it's going into — we'd much rather answer that question before installation than after.

Getting this wrong is the most expensive installation mistake there is. A converter that isn't fully seated will destroy the front pump the moment the engine turns over — and it will do it in seconds. Take the extra ten minutes.

1. Seat the converter into the transmission, not the engine.
With the transmission still out, slide the converter onto the input shaft and rotate it as you push. You're feeling for distinct stages of engagement — the input shaft splines, then the stator support, then the pump drive. On most units you'll feel two or three separate drops. If you only felt one, it isn't home.

2. Verify it's fully home.
Lay a straightedge across the bellhousing face and measure back to the converter mounting pads. The pads must sit behind the bellhousing face — the converter should be recessed, never proud of it. Write that number down; it's your reference for the next step.

3. Check it spins freely.
Before anything is bolted up, the converter should rotate by hand with no binding or drag.

4. Bolt the transmission to the engine — with no help from the bolts.
The bellhousing should come up flush against the block on its own. If there's a gap and the bolts are taking real effort to close it, stop and find out why. Never use the bellhousing bolts to draw the transmission to the engine — that's pulling the converter out of the pump.

5. Re-check rotation after bolt-up.
It should still spin freely by hand. If it's locked up, the converter has been pulled off the pump drive. Separate them and start again.

6. Only now pull the converter forward to the flexplate.
Draw it forward evenly and install the pad bolts.

Target gap: 1/8" to 3/16".
That's the space between the converter mounting pads and the flexplate before you draw the converter forward. Measure it at more than one pad — if it varies noticeably around the circle, something is off before you go any further.

Too much gap and torquing the pad bolts drags the converter forward out of the pump. Too little and you preload the crankshaft thrust bearing. Both fail, and both fail expensively.

If your combination is unusual — a spacer plate, an aftermarket flexplate, an engine or transmission swap — confirm the figure with us before you button it up rather than assuming the standard range carries over.

Once the clearance is verified, torque everything to spec — the figures are in the torque specifications article.

All figures assume clean, dry threads and a correctly seated converter. Verify clearance first — torquing pads onto a converter that isn't fully home will pull it out of the pump.

Flexplate to crankshaft

• LS — flywheel / flexplate: first pass 15 lb-ft, second pass 37 lb-ft, third pass 74 lb-ft
• LT — flexplate to crankshaft bolts: first pass 22 lb-ft, second pass +45 degrees

Converter halves

Assembly torque for the bolts holding the converter halves together. Builder reference — you won't normally touch these in a vehicle install.

• 230 / 252 with TSI aluminum front — 23 ft-lbs
• 230 / 245 / 252 / 258 / 264 / 265 with CDS aluminum front or CDS steel front — 25 ft-lbs
• 258 / 264 with TSI aluminum front — 30 ft-lbs
• 252 / 258 / 264 with ATI aluminum front — 30 ft-lbs
• 252 / 258 / 264 lock-up with M&M aluminum front — 30 ft-lbs

Mounting pads

Converter-to-flexplate pad bolts. This is the one you'll be doing on an install.

• TSI aluminum front, no steel inserts — 50 ft-lbs
• TSI aluminum front with steel inserts (258 / 264 only) — 60 ft-lbs
• CDS aluminum front with steel inserts, or steel front with 7/16-20 — 60 ft-lbs
• CDS steel front with M10 — 50 ft-lbs
• ATI / M&M aluminum front with steel inserts — 60 ft-lbs

If your front cover isn't on this list, ask before you pull the wrench. Different manufacturers use different fastener sizes, thread pitches and insert materials. The wrong figure either strips an insert or leaves a pad that works loose at rpm — and a pad that lets go at speed takes the flexplate with it.

Our converters are custom manufactured and application specific — every unit is built for the combination it's going into, which is why there's a lead time at all.

Per our shipping policy, lead times typically vary based on product line and are currently in the 3–4 week range. More custom options and specifications can lead to longer manufacturing and delivery times.

A few things worth knowing:

• The product page carries the most current time for the specific unit you're looking at. That's the number to trust — this page can't be as current as the listing.
• Component availability moves it. Core supply in particular can tighten on specific diameters, and when that happens it affects build scheduling.
• A dealer may have one on the shelf. If your timeline is tight, that's often the fastest path — some of our dealers stock popular configurations.
• If you need something faster, ask. We'd rather hear about a deadline up front than miss it.

For a date on an order you've already placed, use order status or reach a specialist directly — we won't guess at it from here.

The order status page will pull up your order and its current state, including tracking once the unit has shipped.

You'll need your order number — it's on your confirmation email and looks like S followed by five digits.

If the order is still in the build queue, the status will reflect that rather than showing a tracking number. Custom converters spend most of their lead time in manufacturing, so it's normal for there to be a stretch where there's nothing to track yet.

If something looks wrong — the status doesn't match what you were told, or a tracking number has gone quiet — reach out and we'll chase it down. That's faster than waiting.

We ship regularly with UPS, FedEx, USPS, and DHL, depending on a variety of factors including delivery location, weight, and required transit time.

All converters ship in our custom CDS-designed packaging, which is built specifically to get a torque converter to you undamaged. This isn't a generic box — the packaging is part of the product.

For larger orders and pallet quantities we ship LTL freight rather than parcel.

Internationally, we ship regularly via UPS and DHL.

A signature requirement is added to all orders over $500.

If you need to make alternative delivery arrangements — hold at a location, redirect, or schedule for a specific day — you should have options through UPS MyChoice or FedEx Delivery Manager, depending on which carrier your order shipped with.

Please note that we're unable to make any of these changes for you. Once the package is in the carrier's network, those controls sit with the account holder at the delivery address, not with the shipper. Setting up a free MyChoice or Delivery Manager account before your package arrives is the smoothest path.

We offer local pickup on any of our products.

Where: Circle D Specialties, 5003 Langfield Rd., Houston, TX 77040

When: Monday–Friday, 8:00am – 5:00pm Central

Select local pickup at checkout, and wait for the notification that your order is ready before making the trip — custom units still have to be built, and pickup doesn't skip the queue.

Yes — we ship internationally and do it regularly.

Carriers: UPS and DHL for international destinations, selected by country, weight, and transit time.

Duties and taxes: import duties, taxes, and any customs brokerage charges are the responsibility of the receiver and aren't included in what you pay us. Those are set by your country, not by us, and we can't estimate them accurately.

Packaging: international orders ship in the same custom CDS packaging as domestic, which matters more when there are extra handoffs in the chain.

If you're ordering from outside the US and want to confirm the best routing before you place the order, reach out — for larger or multi-unit orders there's sometimes a better option than standard parcel.

Current pricing lives on the product page. That's deliberate — we'd rather send you to the live number than quote one here that could be out of date by the time you read it.

For an off-the-shelf configuration, browse the catalogue and the price is on the listing.

For a custom build, submit a spec request. It's free to spec, and the response comes back with the recommended unit and its pricing together — which is more useful than a number without a recommendation attached.

For dealer and wholesale pricing, that runs through the dealer application rather than retail listings.

One note for anyone comparing prices across sites: we operate a Minimum Advertised Price policy on Circle D branded products, so an advertised price well below what you see elsewhere is worth a second look.

Yes, we do.

Contact us and we'll provide a coupon code that can be applied to your pending web order. The easiest sequence is to get the order to the point of checkout, then reach out for the code before you complete it.

Thank you for your service — genuinely.

Reach out as fast as you can — timing is everything here.

Before the unit enters manufacturing, there's normally room to adjust specs or cancel. Since every converter is built to a combination, catching a wrong spec early costs nothing but a phone call.

Once the order is in or entering the manufacturing phase and hasn't shipped, our return policy applies a minimum 10% restocking fee on cancellation. That's because the build has already consumed a slot and, in many cases, components specific to your spec.

After it ships, it becomes a return — see the return policy, which requires prior authorization and carries a minimum 20% restocking charge.

If you've realized the spec is wrong rather than wanting out entirely, say so — adjusting a build in progress is often possible and is a much better outcome than a return.

Sales and product questions
sales@circledspecialties.com · (713) 895-8834

Service, RMAs, and units already sent in
service@circledspecialties.com · (713) 895-8834

Hours: Monday–Friday, 8:00am – 5:00pm Central

Address: Circle D Specialties, 5003 Langfield Rd., Houston, TX 77040

Live chat is available on the site during business hours. Outside those hours the chat widget hides itself — email is the right route then, and it gets read first thing.

If your question is about which converter to buy, the spec form is genuinely faster than a phone call, because it captures everything a builder needs to answer you properly the first time.

Whether a core is involved depends on the specific product, so the product page is the authoritative answer for what you're ordering. When a core is required, the requirement and any associated charge appear on the listing and at checkout.

A core return has to be authorized by us before you ship anything. Contact us to start that and we'll issue the authorization through our service portal. Don't send a core back unprompted — an unauthorized shipment arrives with nothing to match it to, which is how cores go missing and credits get delayed.

Once you're authorized:

• Ship it back in the packaging your new unit arrived in. That box is designed for exactly this and it's already in your shop.
• Cores need to be complete and rebuildable to be creditable.

One piece of context that occasionally affects availability: core supply genuinely tightens on specific diameters from time to time, industry-wide. When that happens it can affect build scheduling on the affected configurations. If a core shortage is going to affect your order, we'd rather tell you than let the date slip quietly.

If you're unsure whether your order needs a core returned, ask before you scrap the old unit.

The process is straightforward, and doing it in this order saves everyone time.

1. Submit the service request form. This creates your authorization and tells us what's coming and why. You'll get an authorization number back — it looks like R followed by eight digits.

2. Box the converter up. Use packaging that will actually survive the trip; a converter is heavy and concentrated. See the packaging guidance below if you no longer have the original box.

3. Put the RMA number on the outside of the shipping container — either on the box itself or on the shipping label. This is the step people skip, and a unit that arrives without a visible RMA number can't be matched to its paperwork.

4. Ship it to us via UPS or FedEx only. We're not able to accept service returns via other carriers.

Ship to: Circle D Specialties, 5003 Langfield Rd., Houston, TX 77040

Once it lands, it goes into the queue and you'll hear from us with findings. If a repair quote is needed, you'll get that before any work happens.

Current service turnaround is 7–10 business days, measured from when the unit arrives at our facility — not from when you ship it.

A few things extend that:

• Stall speed changes. Any change to the converter's specification is a build operation, not just a service operation, and it adds time.
• Findings that need a quote. If we open it up and find something beyond the scope of what you authorized, we'll come back to you with a repair quote before proceeding. The clock effectively pauses while that's approved.
• Parts availability on specific configurations.

If you have a deadline — a race, a build that's waiting on this unit — tell us when you submit the form rather than after. We can often work with it if we know about it up front.

It depends entirely on which series you have.

Pro Series — yes. Stall adjustability is a core feature of the series. We can go up or down, and this is a routine service operation. It runs through the same service request process as any other work.

HP Series — no. An HP Series unit doesn't have stall speed adjustability. If the stall isn't right for the combination, the path forward is a different converter rather than a modification, and in many cases that means a Pro Series upgrade.

Not sure which you have? Grab the part number off the side of the converter and send it over. We'll tell you what it is and what can be done with it.

When you do request a change, tell us what the car is doing now and what you want it to do rather than just giving us a target rpm. "It's flashing 4,800 and I wanted 4,300" is far more actionable than a number in isolation — and if there's a datalog, send that too.

You have two good options.

Easiest: let a UPS Store pack it. Most locations offer packaging services. You bring the converter in, they box it properly, and it ships from there. It costs a bit more but it removes the risk.

More cost effective: a heavy-duty moving box from a local hardware store, with the converter well padded and immobilized inside. The failure mode you're guarding against is the converter shifting during transit and punching through a corner — so pad it generously and make sure it can't move.

Either way:

• Ship via UPS or FedEx only — we can't accept service returns via other carriers.
• Write the RMA number on the outside of the container, on the box or the label.
• Keep your tracking number. We can only work on what actually arrives, so hold onto proof of shipment.
• Consider insuring it. A converter is not a cheap thing to replace if a carrier loses it.

Drain the fluid before you ship, and expect some residual — line the box accordingly.

This is the single most useful thing you can do to get a converter question answered quickly. Most diagnoses stall out not because the problem is hard but because the log doesn't contain the channels that would show it.

Channels we need:

• Engine RPM
• Input / turbine shaft speed — this is the critical one. Without it we cannot see what the converter is actually doing, only what the engine is doing. If your channel list has one addition to make, make it this.
• TCC / lockup command and TCC slip
• Throttle position (and pedal position if available)
• Vehicle speed
• Current gear
• Line pressure and converter charge pressure
• Transmission fluid temperature

Captures we need:

1. Idle to in-gear — engine running, shift into gear, let it settle. Shows us baseline coupling.
2. A footbrake / brake-stall pull — load it against the brakes and let it come up.
3. A launch and full pull through the gears if you can safely get one. Street 3rd-gear WOT works if you're not near a track — say so and we'll work with it.

What makes a log unusable: a default channel list. Most logging tools ship with a channel set aimed at engine tuning, and it usually omits input shaft speed entirely. If you can modify the channel list, do it before you log — otherwise we'll be asking you to go do it again.

Any logging device is fine — HP Tuners, AVID, nGauge, factory tooling — as long as the channels are there. Send the raw log file rather than screenshots or a dyno graph; we need the data, not a picture of it.

If you genuinely can't log — a manual valve body car with no data available, for instance — send video instead and tell us exactly what we're looking at. It's a distant second best, but it's better than a description.

First, let's establish whether it actually is off. A few things routinely masquerade as a wrong stall:

• Traction. If the tires break loose on the launch, the converter never fully loads and the number you see isn't the flash stall. This is the most common false alarm.
• Tune and torque management. Timing, torque limiting, and shift strategy all change what the engine does at the hit.
• Fluid level and charge pressure. Low fluid, or converter charge pressure dropping at high rpm, changes converter behaviour meaningfully. Worth checking before anything else — it's free.
• Measurement method. Brake stall and flash stall are different numbers. Make sure you're comparing like with like.

What we need from you:

1. The part number off the side of the converter.
2. A datalog including input shaft speed — see the datalog guide, because without that channel this is largely guesswork.
3. A plain description of what the car does and what you expected.

Once we can see it in the data, we'll tell you straight whether the unit is behaving as spec'd. If it isn't, we'll make it right. If it is spec'd correctly but isn't what you want for the combination, we can do a stall change — that's a normal service operation on a Pro Series unit.

Lockup complaints are usually resolvable from data, and the test is simple.

Compare engine rpm to input shaft speed. If the two go 1:1 when lockup commands, the clutch is physically applying and holding — whatever you're feeling is coming from somewhere else in the system. If they don't converge, or they converge and then separate under load, we have something to look at.

This is why input shaft speed is the channel we ask for every time. A log showing only the TCC solenoid command tells us what the transmission asked for, not what the converter did.

Common causes worth ruling out first:

• Tune and TCC apply strategy. Apply pressure ramp rates and the conditions under which lockup is commanded are tuning parameters. A shudder is very often an apply-rate issue rather than a hardware issue.
• Clutch capacity vs torque. If you're locking at wide-open throttle on a single-disk setup behind serious power, you may simply be past what that clutch can hold. That's a converter selection question, not a defect.
• Fluid condition and level. Both affect apply behaviour.

Send the log plus your part number and we'll read it. If the converter is the problem, we'll say so and make it right — and if it isn't, we'll tell you that too, along with what the data actually points at.

Have your authorization number ready — it's the R-number you received when you submitted the service request, and it's the fastest way for anyone here to pull up your unit.

Service Desk: service@circledspecialties.com · (713) 895-8834

A couple of things that are normal and don't mean something's wrong:

• The clock starts when the unit arrives, not when you ship it. Turnaround is 7–10 business days from receipt.
• If a repair quote was sent to you, work doesn't begin until it's approved. If you're waiting and haven't approved a quote, check your email — including spam.

If it's been longer than the stated turnaround and you haven't heard anything, chase it. We'd rather you asked than sat wondering.

Follow your transmission's fluid specification. The converter doesn't impose a different requirement than the transmission it's bolted to, and the transmission builder's spec governs.

What's worth emphasizing is fluid level, because it shows up in diagnosis constantly:

• Low fluid shows up as converter charge pressure dropping — often specifically toward peak rpm, which is exactly when you need it most. The symptom can look like a converter problem when it's a fluid problem.
• Aftermarket dipsticks are a common culprit. If you're running a locking or aftermarket dipstick, verify it's actually calibrated to your pan and that the level is set with the fluid at operating temperature.
• Check level at temperature, per the transmission's procedure. A cold reading will mislead you.
• Temperature affects behaviour. Cold fluid is thicker, and a converter can feel measurably different on a cold start than it does warmed up. A complaint that disappears once the trans comes up to temperature is often a viscosity story rather than a hardware one.

If you're chasing something odd, verify fluid level and condition before assuming the converter. It's the cheapest test available and it resolves a meaningful share of complaints.

Our published return policy, in full:

• Condition: only unused, undamaged merchandise with all components and hardware as originally provided will be authorized for return, subject to inspection and acceptance by CDS.
• Direct purchases only. We only accept returns of purchases made directly from CDS. If you bought from a dealer, contact them directly about return options — we can't process a return for a unit we didn't sell you.
• Authorization required. Returns will not be accepted without prior return authorization provided by CDS. Don't ship anything back without it.
• 90-day limit from the original ship date from CDS.
• Restocking: accepted returns are subject to a minimum 20% restocking charge. Orders currently in, or entering, the manufacturing phase and not yet shipped are subject to a minimum 10% restocking fee.
• Packaging and tracking: package returns appropriately and keep a record of your tracking numbers. Insure the package if warranted — we can only issue credit for returns we actually receive.

The reason for the restocking charge is worth understanding: these are custom-built units spec'd to an individual combination, so a returned converter usually can't simply go back on a shelf and be sold to the next person.

Returns need to go back through the seller.

We only accept returns of purchases made directly from CDS. If you bought your converter from a dealer, distributor, or another retailer, please contact them directly about return options — their return terms govern the sale, and we're not able to process a refund for a transaction we weren't party to.

This is separate from service and warranty. If the unit has a problem rather than being the wrong part, we can still help you regardless of where you bought it — send it in through the service request process and we'll look at it. Where you purchased affects returns, not whether we'll stand behind what we built.

Handle this in the first hour if you can — carrier claims get much harder with time.

1. Inspect items upon arrival for any damage or missing items. Don't set the box aside to deal with later.

2. If there is any box damage, take appropriate pictures — before you finish unpacking. Photograph the exterior of the box from multiple angles, the shipping label, the packing material, and the item itself. The exterior photos are what a carrier claim actually turns on.

3. Keep everything. Box, padding, all of it. A carrier may require inspection, and discarding the packaging can end a claim.

4. Contact us. We'll assist with any insurance claim.

If something is simply missing rather than damaged, tell us what's absent and we'll reconcile it against what shipped.

The honest version: we stand behind our work, and the way to find out what happened to a converter is to look at it.

How a warranty question actually gets resolved:

1. Submit a service request and get an authorization number.
2. Send the unit in so we can inspect it. Almost every meaningful question about a converter is answered by opening it up.
3. Send supporting data — a datalog above all, plus the part number and a description of what the car was doing when the problem appeared. A log frequently identifies the cause before the unit even arrives.
4. We report findings back to you. If the failure is on us, we make it right. If it's something else — a tune issue, a fluid or pressure problem, an application beyond what the unit was spec'd for — we'll tell you that plainly, along with what we'd recommend instead.

Things that fall outside coverage are the usual ones: damage from installation error, running the unit outside the specification it was built for, contamination from an upstream failure, and modification by someone other than us. If a transmission sent metal through the converter, that's a symptom of another problem rather than a converter defect.

For specific coverage terms on your purchase, see the published returns and warranties policy or ask a specialist — we're not going to guess at the terms of your particular sale from here.

Submit the dealer application form and we'll take it from there.

What helps an application move quickly:

• Business details — legal name, resale certificate, physical location.
• What you do — transmission shop, performance shop, retailer, installer. We work with all of them, but it shapes the conversation.
• What you expect to move and which applications you see most. A shop that lives in 6L80 trucks and one that builds drag cars want different things stocked.

Dealer pricing and terms are handled through the account setup rather than published on the site.

Worth knowing before you apply: we operate a unilateral Minimum Advertised Price (MAP) policy on all Circle D branded products, and compliance is a condition of being an authorized distributor. It's worth reading before you commit.

The dealer locator will show you authorized dealers by location.

Two reasons this is worth checking even if you'd normally order direct:

Speed. Custom converters carry a build lead time. Some of our dealers stock popular configurations, so if your timeline is tight, a dealer with the right unit on the shelf can be dramatically faster than waiting on a build.

Local support. A good shop that knows the platform is worth a lot — particularly if they're also doing the install and tune.

If you're looking for a specific configuration and can't find it locally, tell us what you need and your timeline. We'll tell you honestly whether a dealer is likely to have it or whether a build is the better path.

Circle D Specialties operates a unilateral Minimum Advertised Pricing (MAP) policy covering all Circle D Specialties branded products.

The core rule: any consumer or public advertisement of Circle D branded products must not result in a net price below the established MAP price for that part number. Net price means the price after any advertised discounts. Free shipping or installation may be included at the MAP price.

Scope: all forms of public or consumer advertising — television, radio, print, catalogs, letters, coupons, internet advertising, email solicitations, websites, and online auctions.

Common violations include showing a lowest price with a strikethrough, or otherwise indicating that a lower price is obtainable. For internet advertising, the displayed price must be at or above MAP unless the consumer cannot click through to see the actual price.

Intellectual property: the Circle D name, trademarks, logos, images, part numbers, descriptions, advertising copy, drawings, specifications, test results, instructions, and vehicle application data may only be used as set out in the policy.

Enforcement: violations trigger a notice. If corrective action isn't taken within the stated time, the distributor's account is suspended and purchasing rights are restricted until further notice.

Monitoring price changes and reviewing advertisements for compliance is the distributor's responsibility. The full policy text is the governing document — read it in full if you're an authorized distributor.