Lets talk torque convertor stall speed with a trans-brake

[Intercooler]

I still haven't put my trans back in after snapping the drum but I am close to the point which is what my question is based around. This convertor was originally spec'd for a 61 then I switched to the 70 and the convertor guy said to just give it a try and see. My two trials before the trans loss gave me these results:


-On the foot brake it went up fairly quick to 3k then took a little bit to hit 3200. It was still climbing and I think would have been a battle in the 3400 range.

-On the brake it shot right up to 3100 then edged fairly decent to 3500 when the drum broke. At the 3500-3600 RPM range it was making a bunch of power.

After looking at Louie's video of his car and the comments about needing a little looser convertor so spool time on the line isn't as long it made me think about loosening mine before I put it back in. The convertor guy cautioned me about going to 4k RPM's because of it not being effecient.

Sound like something I want to do or no?

 

[chris718]

i would tend to agree with the information the convertor guy is giving .there are also other factors in this equation also that we may want to examine .the amount of power that is available at lets say at a 4000 rpm launch may overpower the tires causing traction concerns.a convertor that stalls at 4000 rpms can easily flash to 4300 rpm the instant the transbrake is released reducing the amount of feet traveled in first gear before a gear change must be initiated due to the fact that the rpm range has been used up and this can seriously reduce the leverage available in maximum reduction ratio to accelerate the vehicle.the torque multiplication factors of the convertor go down at higher impeller speeds reducing multiplied force generated in the convertor to twist the turbine shaft and ultimately twist the car forward.larger turbos will generate increased stall speed thereby exceeding the stall range previously encountered with the same convertor.stall speed will vary with identical engine /transmission combinations when used with different rear end ratios WITHOUT the use of a transbrake.this is because the higher numerical rear end ratio you have the easier themultiplied force can overpower the vehicles brake system LOWERING maximum attainable stall speed .with a trans brake and identical engine / transmission combinations you will not see an increase in stall speed WITH the transbrake applied ,but may see a slight increase in flash stall speed the instant the transbrake is released.hope this answers your questions.