Torque Converter Stall Questions

[jpowel29]

Installed a brand new Precision converter and fresh trans on Friday. When I ordered the converter I specified that I needed a converter that I could brake stall at a minimum of 2500rpm to properly spool and leave the line. I spent time explaining my set-up with their sales team so I feel confident that we were both on the same page for this order.

I went to a race on Saturday and made a few shake down passes and immediately noticed that my truck would start pushing hard on the brakes around 1850rpm. I got a good data log of the burnout, stage, and launch and the most rpm I could get was 1859rpm at 9.4% throttle position. At that throttle position I am not making any boost and torque numbers are tiny so I couldn't get a decent launch or get up on the turbo at all. We also had just upgraded the entire braking system with EBC yellow pads and freshly turned rotors to make sure that was in top shape.

I plan on calling Precision tomorrow but I wanted to get some opinions on what my expectations should be from the converter. I assumed that I would be able to get a lot more stall rpm than 1859rpm. Are there other issues that could alter/affect the brake stall? The converter locked up right at the top of second gear and the trans is also working fine (no codes).

The part number on the converter invoice from Precision is 303438-3HS. Has anyone else ran this converter?

I have a SC 1055 that I can swap in but I wondering if there is something that I am simply overlooking.

 

[TrentNell]

I have the 2700 stall in my truck and here is a screen shot of how much RPM i am getting on the line . with a 2wd John are you breaking the rear tires before 2k or actually pulling through the breaks ?


the first one is AZ the next one is CA and think the converter needs to be sent back in , doubt it should stall to 3200 but will have to send it in after this next weekend .

 

[jpowel29]

With a decent burnout I could get my old Goerend up to 2100rpm before pushing through the brakes (I believe it was either a 2200 or 2400 stall).

I am pushing through the brakes (sliding through the beams)

 

[TrentNell]

With a decent burnout I could get my old Goerend up to 2100rpm before pushing through the brakes (I believe it was either a 2200 or 2400 stall).

I am pushing through the brakes (sliding through the beams)

there has to have been a mix up or mistake on the stall , last we talked i thought you were going with the 2700 stall ?

 

[jpowel29]

that is what i asked them for....

 

[bullfrogjohnson]

I have the 2700 stall from precision also and i can stall to 2k in 4lo so i know I can get at least 2700 in 4hi.

 

[dmaxfireman]

maybe you need a higher stall since they are basing that 2700 on 4 sets of brakes holding it back instead of two?

 

[Rhall]

Have you ever tried a second gear launch? It might be the key to making a higher boost launch, yet smoother with the 2wd trucks.

 

[paint94979]

Have you ever tried a second gear launch? It might be the key to making a higher boost launch, yet smoother with the 2wd trucks.

Smoked converter... its what's for dinner

 

[jpowel29]

I haven't tried a second gear launch while racing - only on the street and it acted strange. Not sure I had the tcm tuning correct for it however.

 

[Rhall]

Smoked converter... its what's for dinner

Yeah, thats what people say, i did it for a whole season of sled pulling, with a converter that was in my truck for 3 years. Ill see how my 1053 holds up this year to some launches hooked to the sled. Not sure what gear yet, but it wont be first.

 

[Stingpuller]

Stall Speed

Tuning and turbo play a BIG part in how a convertor will stall. A convertor works on how much TQ is put to it. It will stall different with two different power curves. You will need a VERY loose convertor being it's 2wd and it's going to be harder to bring it up. Just a for insteance my truck now with a 1055 and a stock motor(turbo=everything) will stall very high and leave the line with 32 lbs. of boost. The funny thing is you can stage and bring it up almost instantly! I also think you would benifit from a second gear start. 2wd and lots of TQ don't need all that gear on the leave. If your going to send the convertor back anyhow I would try it and see what it does for your truck. Jeff

 

[Kat]

Yeah, thats what people say, i did it for a whole season of sled pulling, with a converter that was in my truck for 3 years. Ill see how my 1053 holds up this year to some launches hooked to the sled. Not sure what gear yet, but it wont be first.

Exactly... Drag racing or sled pulling I have 1st removed. It's a 1057 :thumb: I know I could fry it. But, the extra 2/10th's is worth it me.

 

[JoshH]

I wonder how difficult it would be to put some sort of pinion brake on the rear axle to help keep from pushing through the brake.

 

[dmaxfireman]

I wonder how difficult it would be to put some sort of pinion brake on the rear axle to help keep from pushing through the brake.

machine a rear cover to hold another pinion to the ring gear and then weld the brake rotor to the end of the pinion and fab up a bracket to hold the caliper.


one day i am going to try and make one of these for a different purpose (tandem axles)

 

[jpowel29]

I wonder how difficult it would be to put some sort of pinion brake on the rear axle to help keep from pushing through the brake.

Been talking about that very thing - you wouldn't have to fight against the gear reduction that way.

 

[Mike L.]

machine a rear cover to hold another pinion to the ring gear and then weld the brake rotor to the end of the pinion and fab up a bracket to hold the caliper.


one day i am going to try and make one of these for a different purpose (tandem axles)

It will never hold at the tq we produce. trans brakes won't work either; they will wipe out a converter. Already been tested.

 

[dmaxfireman]

bummer so one would have to make a custom heavy duty housing then? or you mean the brake won't back the tq?

 

[Mike L.]

You can't hold these brutes with a driveshaft brake and a trans brake will destroy the converter.

 

[Noreaster]

could try adding 2 more calipers out back