67mm turbo Supra transmission Questions

[emericaskater285]

I recently bought a built 7mgte supra with a 6776 bolt on ball bearing turbo with a SP built a340 transmission.

What I am trying to figure out is what people are using for higher stall torque converters for the a340 transmissions. Really would like to know if it is possible to get a stock torque converter modified to stall out over 3200-3500+ rpm or so. I am thinking that would be the sweet spot for this turbo and still be very street-able.

Right now my stall speed is 2800-2900rpm and will build about 5psi (wont go any higher) if I really sit on the stall with the ebrake up and brakes down as hard as possible. When I let off the brakes it still feels very laggy and slowly builds boost. I know the turbo is a little large and is part of the problem, but it matches the motor pretty well once into boost.

Any help with this is appreciated, I have been searching around and haven't really heard of anyone re-stalling a stock converter to much over 2800rpm. I am not worried about the street-ability of the stall as I have been in much higher stall cars and it isn't too bad imo, and it isn't going to be driven every single day.

 

[Nick M]

What trans fluid are you using? If you have Dex 2 or 3 as Toyota suggested it is likely conventional oil and if you heat it by power breaking, the fluid will lose viscosity. The torque converter heats the fluid rapidly, easily above the 200 degrees it is designed to operate at.

I would say Dex 6 which is synthetic, but it is costly to say it is Dex 6 as it is a GM trademark. Ashland oil, aka Valvoline has a synthetic fluid that is Dex 6 and Mercon SP compatible. Synthetics eliminate the Ford viscosity issues in the torque shift trans.

Heating your trans fluid could be causing a problem if you think it is laggy. Although hitting 5 psi while standing still is pretty good on a turbo that big. Your stall speed is reasonable. IPT trans will redo the converter for you.

 

[super51fan]

You need a trans temp gauge if you don't have one . Long "brake torqueing" really raises trans fluid temp quickly. ATF fluid looses it lubrication ability at geometric rate as temp raises. I feel Amsoil ATF is some off the best on the market at a fair price. It looses the lubrication ability slower than most fluids on the market. IMO..

I bet SP remembers the build and could get you specifics. Your torque convertor stall speed is probably higher than 2700 2900 rpm. With a turbo car it is harder to "flash' your torque convertor. Your big turbo won't help either. Have you paid attention to rpm at say 40 mph wot and let the trans downshift. If you have the turbo response this may give you a more accurate stall speed idea.

With stock size convertor probably 3400 rpm is about all you can get. IMO Good luck watch that trans temp, get new fluid in there asap.

I bet your car is fun to drive.

 

[Nick M]

Keep opinions like scAMS oil to yourself, it will help the site. Synthetic fluids don't have a problem with temps.

 

[emericaskater285]

I do have a trans temp gauge, but not installed yet. Its got a big cooler on it with a fan etc. The car is set up very well. its very fun to drive, just want it to be quicker off the line.

the invoice said 3200 stall, but it doesn't have any more in it than 2800 rpm. I haven't changed fluid yet, but is on the list of things to do. (i work in parts at a GM dealer so its not a big deal) Also don't really launch the car every time, just have a few times here and there.

 

[TurboStreetCar]

Stall is relative to power input. It could very well be rated at 3200 but if your not making the same power they rated it for it wont make it there. I had a SIP 3500 stall in my car when i had the 7M (i actually still have it now that i think of it) and it only really made it to 3200. Wasnt quite enough for the Masterpower T70 i had on the car. Same deal it would make like 5-8psi boost but the motor didnt really make any power untill 10+ so it was sluggish off the line.

You can have a stock converter restalled. Your kinda far away from here (NY), but google ProTorque. All the really really fast guys use them. They make awesome converters and the guys that work there are pretty cool.

I ran Amsoil synthetic ATF in my car when i had the a340e, it had the IPT master rebuild kit in it. Thats the fluid IPT recommended. IIRC it was 14 or 17 a quart. Kinda pricy.