VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc How Interchangeable is one Powerglide for another?

I would like some experienced input here from the trusted folks on the panel. Engine refresh was done over the summer (bad timing for shows and cruise-ins) and now it's time to address the leaky Powerglide in my '58 Bel Air. It has to be done, it's been bleeding all over the drain pan on the garage floor and can't cruise more than a few miles without needing a top off. It also starts to smoke and mis-shift after a short cruise and it's quite possibly toast inside.

I have some opinions of the tranny repair outfit that said they put in a seal kit for me 2 years and less than 500 miles ago (starts with and "A" followed by an "a"). I'm not going back to them, but the PG I have is painted blue, which is their identifier of a rebuilt replacement, in this case dating back to the '70's when Grandma was still driving the car.

So here's what I have to work with: PG in the car now is not original, is blue, cast iron (I think, though I haven't lifted it), leaky and of doubtful mechanical operability.

I have an aluminum Powerglide that was given to me, taken from a Nova that I'm told was driven onto the lot where it was parted out. Engine and tranny came out together, engine was used for another vehicle by a friend who bought both as a set, tranny was not needed, so it has been sitting under a cover for 3 years. It has fluid in it that is not leaking onto my garage floor.

I have a brand new seal kit to put into whichever one I use, which will also be checked out internally and/or rebuilt, but there are questions of which of the two is best, or if the aluminum one will even work without modification. From what I've read, a Powerglide is not the same across the decades and models of it's historical applications.

I'd like to use the newer one if I can. Will it bolt in? Will it require more than simple modification? Would it be a big improvement? Will the newer Powerglide be considered an unacceptable replacement for the older unit of the same name?

Thanks for your suggestions!

-Pat.

I would attempt to fix the iron PG first.Would determine just where it is leaking from.Front pump seal and converter O ring most common.Will leak out of the little opening at front of case,partly covered by little tin piece.Also could be leaking from servo cover.The large casting on right side.Rear seal can also leak where drive shaft yoke is...easy fix.Are the cooler lines leaking?The slipping could be caused by low fluid,plugged screen (with clutch plate material-bad)...or a leaky modulator can suck fluid out of the transmission and burn it (exhaust smoke)...Would be best to determine what is leaking.....slippage could be worn clutches, improperly adjusted low bad or worn out low band.

The Aluminum PG from a Nova-what year?If it was a 6 cyl will have a light duty clutch pack and if pre-1968 it will be air cooled.The Alum PG will perform excatly the same as the cast iron.Low has the same ratio (1,82)..it up-shifts once at the same speed.It is about 80 pounds lighter.Front drive shaft will need changing.Starter is mounted differently and a different starter housing is require.All shifting and kick-down linkage is different

Thanks Gene, it sounds like the mods would make the free transmission (it was from a V8, I believe a 327, and it has cooling lines much like the older one) almost as difficult as repairing the old one unless the starter mount and linkage will transfer over. Leaks are possibly from all of the above, which the seal kit should take care of, and the smoke odor (not actually seeing smoke from the driver's seat) is probably the low band which I imagine would be replaced regardless.

The extent of repair required for the old one will be the determining factor, I think. I get a good rate on parts and labor, but I'll have to get it penciled out to see what's more affordable. Then again, if parts transfer over and the forward half of the drive shaft is easy to get, I could live with the performance bonus.

Good thing I'm not in a hurry to get this done. After considering the preservation versus performance, I think I'll try for a win-win with this PG swap. If my tranny shop can locate a replacement for the front section of the driveline, I'll have them keep the original front driveline section with the cast iron PG so that it can be restored to original appearance at a later time. This way I won't be making any changes that can't be undone.

If it was my car I would look for a 1959-62 cast iron PG from an 8 cyl. car.This would have all the improvements that the 1958 troublsome PG needed.There were several up-dates necessary to make a 1958 unit half way dependable.Then I would have the newer unit rebuilt and install it with no other problems.
The aluminum PG will require different shift linkage and kick-down linkage ans well as the starter drive housing will need to be changed to mount the starter.....good luck on finding the proper alum.PG shift linkage to fit a '58.
Driving down the road there is NO difference between the iron and aluminum PG...They both shift the same and have the same gear ratios in low range (unless you get one from a 327 engine).There is no real advange to the aluminum unit except the lighter weight.

I deferred to the old pro at the tranny shop who said basically the same thing you did Gene, - we're staying with the cast iron PG that's in it mainly because of what you point out here. Too many mods required for too little improvement, if any. The one that's in it was a rebuild installed by a national chain shop back in the early '70's. Hopefully they knew about the problems and were installing the updates by that time, or using cores from '59 to '62.

Which brings up another question - it's blue now, (the chain shop's identifying color) what color should it be from the factory? I have an empty space on my color reference chart up until the aluminum case years. Would the cast iron have been left unpainted, black, orange....? Is this one of those "paint it the color of unfinished cast iron" situations?

-Pat.

The iron cases were unpainted but due to rust etc. black is accepted now days.