Stock Powerglide case cracking in the reverse curcuit

[HR 9505]

I'm currently on my second stock powerglide case that has split or cracked in the reverse circuit and leaks bad when the transbrake is applied. I have run stock cases for years with no issues but I had one to crack last year and now this one. I know these cases are 40 years old and it's basically a crap shoot whether you got a good one or not. I was wondering if there is a main reason why these things crack in this area or could I have an alignment issue. I'm running a 3500# 55 wagon with a SBC 406 on alky running 6.30's and 40's wide open. Could I be at that fine line of power vs weight that could be causing this? Before I found another stock case, I wanted to see if going to an aftermarket case would be better fit?


Thanks in advance!
Jason

[STK1217]

Jason

How is your engine and transmission mounted to the frame?

[Tom Goldman]

X2 on mounting.
Case cracking in this area is usually due to flex in mounting , lack of a mid plate ,and engine limiters. .....Just gets worse when you apply more power.
I just had a customer with a stock mounted LS engine with a glide experience the same problem . got away with it until he boosted the power.
If you already have a mid plate and limiters, do not use a solid trans mount , as there can still be enough flex to crack a stock case. Driveshaft alignment should also be checked .
Bottom line , stock cases are at least 40 years old , many may have been in wrecks and subject to unknown stress before being used for racing. ...They have served valiantly ,but are very weak compared to the aftermarket cases .

[SGSST109E]

Make sure your drive shaft isn't bent. A common cause of cracking in the rear of a pg case.

[HR 9505]

In response to the mounting here is what I have. I have solid motor mounts up front (no front plate but they are solid mounts bolted to the front of the motor), no limiters and I'm running a stock style rubber transmission mount on the rear.


I will check drive shaft alignment and also have the shaft checked for straightness.


Thanks!

[HR 9505]

Also....as far as driveshaft alignment goes, is there a maximum number of degrees down between the tail housing and the driveshaft I should have? What would be considered "misaligned" I guess is what I'm asking?


Thanks!

[Tom Goldman]

If your car sets high in the rear , it may be advisable to lower the rear crossmember or raise the front of the engine.
I would never want to see more than about 4* on the front, especially if the car is a leaf rear suspension.