What stall are you guys using?

[Svtfreak]

I’ve got a 6r80 behind supercharged coyote. I may have to change my converter. Currently have a factory mustang converter. It was tight, but worked pretty good before something failed. I could nitpick and say I wanted it a touch looser. When you release the brake, car moved quickly and I’ve since changed to manual brakes. Everything so far points to it. So since I have to change, I’m thinking of going with a yank or circle d and getting one a little higher than stock. So, what you guys using? Keep in mind my trans first gear is like 4.17, 2.34 2nd. Very low. 3.55 rear gears. The idle speed is raised some due to the blower tune, about 800 rpm or so, 1000, maybe 1100 cold. Thanks y’all.

[HVACMAN]

I have a 3000-3400 stall behind a 495HP LS3 with a 4L70E & 3.73 gears. It has a 3.06 first and .70 OD.

[Svtfreak]

Thanks hvacman.

How’s the flash off idle? When you release the brake, does it start creeping on its own or require a touch of throttle?

[JimLev]

LS3 with a 4L65e tranny, 3.55 gears. I'm using a 3000-3400(?) stall speed converters that was spec'd for a 4L70 tranny.
I have to ever so slightly touch the gas to get the car to move.

[HVACMAN]

Thanks hvacman.

How’s the flash off idle? When you release the brake, does it start creeping on its own or require a touch of throttle?

At idle it will barely creep but I attribute that to engine lope.

[Svtfreak]

Thanks guys. I know the torque profile of the coyote is drastically different so my thought of going a little lower than y’all have should yield it just right. Gonna run that by the professionals first for confirmation

[Gordon Levy]

2500-2800

[Bob Cowan]

Stock is about 2,800, as far as I can tell. The stock torque converter is "only" good for about 500'ish hp or so. More than that and it won't last very long. Some people said stock works great. And some people say it doesn't. Since I already owned it, I initially used the stock converter just to see how it worked.

There were a few things about this that really bugged me:
-- the 1-2 upshift was pretty harsh. Almost like a kick in the bu tt. Some custom tuning improved it, but still pretty harsh.
-- Apparent poor brake function. In Neutral, the brakes work really well, and feel great. In Drive, not so much.
-- speaking of brakes, any little bit of sand or water, and the front tires would lock up and slide before the car stopped.
-- Shifting from Park to Drive was a bit of a bang.

I purchased a new torque converter from Circle D Specialties; lock-up, triple disc, billit construction, yada, yada, yada. Stall speed 3,200-3,400. I took it to a trans shop to do the swap because I am unable to do that kind of heavy lifting at the moment.

I'v probably driven the car only a few hundred miles with the new converter. And it's a HUGE improvement! Almost all of the annoyances mention above have resolved. When you let off the brakes, the car starts moving. It doesn't jump, it just starts moving. A lot like my truck. The 1-2 shift is significantly improved. And the other shifts are almost imperceptible, even when hard on the throttle. Stopping on water or dirt is much easier. The car is now significantly easier to drive.

I think I wouldn't be afraid to try a slightly higher stall speed; like 3,400-3,600.

My car has an oil temp gauge. Since I don't race it, I don't really need that. In 5,000 miles, the oil temps have stayed pretty close to water temps. So I changed it to a trans cooler gauge. So far, I have not seen the temps much above 50*C. But it's been pretty cool lately. We'll see what happens in the summer.

[Skfunk]

put a 3000 stall behind Blueprint crate 306.

[Svtfreak]

I put in an order for a yank 3400 yesterday, after speaking with them for awhile. He said his 3400 actually may be a little tighter than others so we shall see.

[NAZ]

Been hesitant to weigh-in on this as some folks just seem to dismiss anything that doesn’t fit their pre-conceived ideas, regardless the fact they have no real experience with selecting converters. Drag racers know that selecting the right stall can have a dramatic affect on performance. That goes for dedicated race cars and street / strip machines that have to have good street manners.

First a little bit of info on stall speed. Stall speed is influenced by many factors and even the weather and density altitude can affect the actual stall speed. Don’t expect to order a particular stall speed and actually see your converter stall at exactly that speed. This is especially true if you picked one out of a catalog or purchased one without providing all the relevant information about your engine, trans, rear gears, weight, and more. A shop that builds performance converters will ask a bunch of questions and bake all those answers into a formula to determine what custom converter will likely work best for you.

Another thing about stall speed, if you run a 4000 RPM stall converter that does not mean the engine will always run at 4000 RPM or higher. At WOT from a stop light yes. But cruising down the highway, no – it just doesn’t work that way. And if you have a lock up converter, the engine and trans will be directly coupled when the trans controller sees pre-programmed conditions and the engine will act as it would with a stick, no slip.
Most people tend to select a stall speed much lower than what would give the best performance. For a street only car I want a stall speed no lower than ~500 RPM below the peak torque RPM. I run a 6000 RPM stall in my car on the street – no problem. But for most of you out there, I suggest you discuss this with a reputable custom converter builder and go with their suggestion. ATI, FTI, and Hughes are well known performance converter builders.

You should test your stall speed (flash stall) to determine your actual stall speed – don’t assume it’s close to the advertised. This is important and it’s a simple test, see the attached video.

And for those that run 500 HP or more, make sure you discuss the type of sprag the builder plans to use. The sprag is the weak link in any converter and 500 HP (more specifically, 500 lb ft torque) seems to be about the max you can expect some to survive. Some builders have HD sprags that claim can hold up to more power. Make sure you discuss this with the builder.
Below you will find links to sites with more info:
https://www.badasscars.com/index.cfm/page/ptype=product/product_id=78/category_id=62/mode=prod/prd78.htm
http://www.tcsproducts.com/media/1/TCS_How_To_Select_the_Right_HiStall_Converter.pdf
https://www.youtube.com/watch?v=4NDvsgheq-8&list=PLBXvzd5ICqLWa1pH3li6L6p_M6nrpka1R&index=6&t=0s

[Svtfreak]

Naz, you’ve posted that before. Or someone has. Maybe on another thread.

I can’t test my stall speed currently like you say. It won’t stop. The rear wheels will not stop. So I can’t find out where it flashes as it acts like it’s always already flashed at idle. Everything has been gone through. The brakes, the valve body and all solonoids have tested ok. Cooler lines clear and flowing well, computer hooked up, locked up, unlocked, slip is measuring and changing with brake application. The rear wheels slow but will not stop. There’s more but I think the picture is set.

There was a small amount of super fine dust in the pan. The trans guy things it was from the converter. He thinks it’s not fully unlocked. I know zip about the inside of a converter but I gather there’s a clutch in there and it’s dragging. Not fully unlocked. So after doing everything short of rebuilding the trans, it’s time to swap the converter. In the mean time, I found someone else who had a VERY similar issue. Same trans, better brakes, better tires. A higher stall solved his problem and made it drive better. Mine worked when it was warm, tires sticky, floor clean and this started when cold, tires hard and floor full of body work dust.

I’ll update once I swap the converter (and I’ll even try the flash test to see where it does) and cut open the converter that’s in it to see what happened. If anything.

I appreciate that info, naz, but it comes back to I can’t get it to do that test cause at idle it’s already doing what the tests goal is to make it do to read the rpm.

I had a very long conversation with the converter builder also before electing this converter.

Keep in mind this is the factory mustang converter. It’s for a 4000lb car. I’m at prolly 1800lbs maybe right now. It feels tight in the mustang. I knew the possibility of having to do this from the get go, being the first to run this setup in this car. I went on a recommendation from one person that the stock mustang one would work knowing there was a good chance it wouldn’t. It did, for a bit, but seems if things aren’t just perfect, cold tires, dust or gravel on road, etc, that it just might be too tight

[NAZ]

Yes, that was me that suggested you check the flash stall speed and I provided a link so you could learn how to do that. It’s important to know this from the get-go for troubleshooting issues later. And you informed me that you can’t check the stall because the brakes won’t hold the car back. Just to be clear for others reading this, flash stall is not determined with foot braking the car – it’s typically done from a slow roll and many times in a higher gear so the RPMs don’t race past the flash so quickly. If the brakes won’t stop the car the test can’t be completed as that is a safety issue. Now I'm not suggesting you do something unsafe but if it was me, I'd put the trans in neutral when coming to a stop. Back into gear and from a slow roll hammer the throttle and note the flash speed. Test completed.


I also suggested that from your symptoms and the claim that it worked OK before, it sounds like a failed sprag which you immediately dismissed. Not sure you’ve ever had one fail but I have and the classic symptoms are a dramatic reduction of stall speed, brakes may not hold the car back and acceleration from a stop is very lazy. If you’re not sure what a sprag does, look it up, you should really understand this important part when trying to troubleshoot a converter problem.


I then bid you good luck on your search for a fix. I sincerely meant that and still do.


My hesitation in my latest response was because it is clear I can’t help you and it would be simply a waste of time to try and offer advice you’re not ready to hear.


But then I thought about it and decided that when we start a thread and post a solicitation for help it really goes beyond the OP. There are others out there reading this and either have a similar problem or have heard of this problem and want to know how to avoid it. Some will post and some will simply follow along. It was in this spirit that I decided to add information on a subject that I have been formally trained in at the FOMOCO Engineering Center as well as many years of experiential learning so that others may consider this new info with all the other sources of info on the subject. And maybe, by following the links some will learn a bit more about an obscure subject most give little thought to.


I don’t consider it a hijack of your thread; it is original subject matter info offered to you and others reading this. You stated that you have little knowledge of converters, if you follow the links I provided you will start your self-education on the subject. With knowledge we make better choices, rather than simply throwing parts at a problem. Use the info I provided as you see fit. Or challenge it if you disagree. You won’t hurt my feelings and I have no dog in the fight. But if you ask for help and summarily dismiss it enough times you might see a decline in assistance at some point.


So again, good luck and I hope you find a fix sooner than later. If you have the converter cut open have the sprag closely looked at by a competent converter builder. The vendors mentioned in my post above are industry leaders that build thousands of custom converters, not all shops have applicable experience in hot rods and performance cars like we build.

[Svtfreak]

Naz, I do appreciate your input and in fact did look to see if I could do that text when you posted it. The brakes where a problem, but even with no rear brakes, you should be able to put a car against a tree, let off the brakes and the rear tires not spin.

As far as the sprag, I don’t recall discounting that. I do recall a discussion about too much power, but I haven’t put hardly any power through it. If something is broken, it’s not cause of being stressed due to too much power. Yet... lol If I did, it was because I didn’t know about one in the converter. I have since learned and that could be it then. Well find out when we cut it open. The difference between it working before and then not could also be explained by other things after i met someone with same problem.

Please know I was not blowing you off. I do appreciate the links you gave.

[Muggstang]

I am using a stock first gen 5.0 Coyote (420 hp 360 foot lbs) I will be driving it on the street only. I am wanting to purchase a 4r70w transmission but I need to know which converter to purchase. The builder is confident that 2500-2800 will handle the demands of this combo. FFR told me the other day that I needed 3200-3500. What is
recommend?

[sread]

I'm pretty sure that you will find that the guys who have been there and done that would recommend going with 32 - 3500.

[Svtfreak]

I am using a stock first gen 5.0 Coyote (420 hp 360 foot lbs) I will be driving it on the street only. I am wanting to purchase a 4r70w transmission but I need to know which converter to purchase. The builder is confident that 2500-2800 will handle the demands of this combo. FFR told me the other day that I needed 3200-3500. What is
recommend?

I have a coyote and 6r80 and just went to a 3400 stall. It works pretty good so far. I have 96 mustang rear brakes, and still go cart stage. Once all the weight is on and the big brakes on, it should
Be perfect.

[narly1]

OK I just spoke with Chris at Lentech and ordered a torque converter for my specific 302 build and AOD transmission combination.
Based on the torque/hp dyno results from an almost identical build and predicted vehicle weight of 2200-2400 lbs he suggested their 7902-CONV-11SS which is 11.25", 2200-2400 stall speed, coupled spline unit.

Earl