Dougs 90

What happens at the stall speed? How do I figure what I need for a stall speed? How do I judiciously choose a Torque Converter for my needs? Does the stock one lock up?

Thanks
Doug

vader86

The stock one in the 90 locks somewhere around 1500rpm.

The TC kinda acts like a clutch, and when it locks it sends all the power thru the driveline.

Where you want it to stall depends on the engine combination you want to run, something like 2000-2200 for a stock L98 is great, but for a more modded engine youll want 2400-2600 at least. Ideally you would like the stall to be as close to the torque peak rpm so the car will launch harder.

Also if its going to be driven daily or frequently, you would probably want it below 3000, lockup can mess with your head over that point because the tranny will feel 'loose' and like its not running quite right. But you can try it if you want the best ETs.

65Z01

The basic TC has to components: the driving element connected to the flywheel and the driven element connected to the tranny input shaft.

At idle and up to stall RPM there is slippage between these two elements; at or near stall RPM the two elements no longer slip very much and begin to move as one.

You can get some idea by rolling along at low speed and popping the accelerator; the RPM to which the tach immediately jumps is the flash speed which is close to the stall speed of the TC.

Our stock TC has an internal clutch so is of the lockup type. When the ECM commands the solenoid to engage this clutch the two TC elements are locked together. With a 700R/4 tranny fluid cannot flow to this clutch even if the lockup command is issued to the lockup solenoid.

My stock TC had a 1,500rpm stall speed; when the tranny was recently rebuilt I had a 2,000rpm stall lockup TC installed. This is the stall speed of the TC in an '85 Vette and works well with street tires. This allowe me to launch at about 1,700rpm but requires a tight track before I can hammer the throttle; on the street I realy have to roll into the throttle on a hard launch.

steveelsbury

Same here - my TC stalls at 2700 and if I load it up by power braking, it simply lights up the tires! This is where driving skill comes in - giving her the max throttle you can without breaking traction! Still learnin'......

It took some getting used to after upgrading from the stock TC, as the car seems to have to rev so high before she starts moving.

Steve

Bluevette85

I believe the 85's stall is 2400, at least mine is.

65Z01

Ah, I've not seen the actual numbers on the '85 TC stall but a guy who runs an '85 Vett at Raceway Park told me his TC stall was ~2,000rpm.

Since he was pulling mid 1.8x 60' times and I was pulling low 2.0xs, it seemed just right for my needs as I race on street tires.

BTW, the guy who did my A4 told me that, even if she holds, I should launch a few hundred RPM below stall as the fluid gets very turbulent close to stall and so torque multiplication drops off. I've found that 1,700-1,800rpm works best for my setup.


[Modified by 65Z01, 12:28 PM 5/25/2003]

vader86

Stock lockup on the 85-86 TC is 2024rpm.

I just tested it today, and it locks at 2000 on the tach, which doesnt give numbers past the 1st two digits.

tpivette

i have the GM 2500 stall converter. a few other members here use this converter also with good results. it greatly improved my 60ft times. however, with a looser converter alot of shops recommend a shift kit. when you install a higher stall speed converter, it tends to draw out the shifts a bit over stock, and a shift kit firms them back up again