TH 400 sprag ????'s

[Sam Colalillo]

How does the sprag mysteriously break in a turbo 400 ? I know hammering the throttle on off while in first gear is hard the sprag . Are there components available which remove the sprag completely from the transmission ?

I know there are several guys making big horsepower that have gone through several sprags . I am hoping to here from these guys on what they did to eliminate the problem. Also hoping to hear from some transmission experts.

Help me understand the weakness of the sprag.

 

[chris718]

here is the answer pics are at the link below www.CKPerformance.com

When researching or shopping around for a GMTH400 transmission or parts you will commonly come across the description "high performance 34 element sprag and drum assembly".This is a factory part that was used in the early GMTH400 transmissions as well as the newer GM4L80E transmissions.Although this is much stronger than a stock spring and roller clutch assembly it does have its drawbacks.This industry accepted urgrade gets in trouble at 750 horsepower/750 foot pounds of torque,especially in drag cars with a transbrake or manual valve body that uses a fixed high line pressure.As a matter of fact this is usually the only item that needs to be periodically replaced on most properly race prepped GMTH400 transmissions.When the sprag fails the transmission will no longer have second gear.Are you tired of intermediate sprag failures and the maintenance and down time they cause? Our in house CNC machined Super Comp Direct Drum and Oversize Sprag Assembly is the answer. This custom drum assembly is fitted with oversize tool steel inner and and outer sprag races ,an oversize 36 element sprag assembly,and a custom sprag retaining plate and spiral lock ring.Special machining of the outer race delivers a constant supply of lube oil to the sprag assembly. All this translates into a drum that can handle up to 2000 horsepower/2000 foot pounds of torque reliably.Due to the larger outer sprag race this assembly comes with custom set of 4 intermediate frictions,4 intermediate steels,a modified pressure plate and a heavy duty snap ring.

 

[Alky V6]

Chris has the answer right there. The new intermediate sprag setup is a godsend from above for 400 users. Well worth the expense. I went through 3 sprag assemblies before forking out the bucks for the real fix. One of the failures occurred on the first run after I repaired it.

The strain on the sprag happens from torque spiking in second gear. Not first. When doing a wet burnout, always start in second and quickly shift up into third and finish your burnout in third. That is the best way to keep from spiking the intermediate (2nd gear) sprag.