Stock Powerglide case cracking in the reverse curcuit

HR 9505 · 04-14-2016, 08:35 AM

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 · 04-14-2016, 05:22 PM

Jason

How is your engine and transmission mounted to the frame?

Tom Goldman · 04-14-2016, 08:18 PM

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 · 04-14-2016, 10:11 PM

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

HR 9505 · 04-15-2016, 08:23 AM

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 · 04-15-2016, 08:28 AM

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 · 04-15-2016, 11:05 AM

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.

04-14-2016, 08:35 AM	#1
HR 9505 Junior Member Join Date: Dec 2011 Location: Greenville, NC Posts: 18 Likes: 0 Liked 0 Times in 0 Posts	Stock Powerglide case cracking in the reverse curcuit 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

04-14-2016, 05:22 PM	#2
STK1217 Member Join Date: Nov 2006 Posts: 133 Likes: 43 Liked 8 Times in 6 Posts	Re: Stock Powerglide case cracking in the reverse curcuit Jason How is your engine and transmission mounted to the frame?

04-14-2016, 08:18 PM	#3
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,454 Likes: 821 Liked 776 Times in 221 Posts	Re: Stock Powerglide case cracking in the reverse curcuit 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 . __________________ Tom Goldman 1500 SG , 1506 STK

04-14-2016, 10:11 PM	#4
SGSST109E Member Join Date: Jun 2007 Location: NJ Posts: 349 Likes: 55 Liked 127 Times in 61 Posts	Re: Stock Powerglide case cracking in the reverse curcuit Make sure your drive shaft isn't bent. A common cause of cracking in the rear of a pg case.

04-15-2016, 08:23 AM	#5
HR 9505 Junior Member Join Date: Dec 2011 Location: Greenville, NC Posts: 18 Likes: 0 Liked 0 Times in 0 Posts	Re: Stock Powerglide case cracking in the reverse curcuit 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!

04-15-2016, 08:28 AM	#6
HR 9505 Junior Member Join Date: Dec 2011 Location: Greenville, NC Posts: 18 Likes: 0 Liked 0 Times in 0 Posts	Re: Stock Powerglide case cracking in the reverse curcuit 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!

04-15-2016, 11:05 AM	#7
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,454 Likes: 821 Liked 776 Times in 221 Posts	Re: Stock Powerglide case cracking in the reverse curcuit 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. __________________ Tom Goldman 1500 SG , 1506 STK