62-66 aluminum powerglide

[ray anthony]

Any help will be greatly appreciated. I have an aluminum powerglide that bangs on the down shift and works perfectly fine on upshift. From a previous discussion board posting I checked the vacuum, replaced the modulator canister,adjusted the idle, and verified that the modulator valve moves freely.

I was just told that I should have three parts : a valve ,a small spring, and a pin which fit into the modulator hole in the tranny. I do not have the small spring. since this spring seems to be what will solve my problem, so I am told.
I would like someone to agree or disagree. If you agree do you know where I could find one. I have already emailed many sources on the internet with no luck. Sorry for the length of the posting but as you can see I am in trouble. Thank you for any help you may offer.

[Bob R.]

Re: 62-66 aluminum powerglide

There is someone in Needham Massachusetts who sells rebuild kits for powerglides. I can't think of his name. He use to run an ad in the Hemmings Motor News. Go to Hemmings site and search under powerglide his name should come up. He may have the part you're looking for.

[Michael H.]

Re: 62-66 aluminum powerglide

Ray,

The spring that you refer to, if missing, is indeed one of the items that can cause a rough downshift. If I remember correctly, this spring was added in production some time in mid 63 because of the problem you describe. It was part number 3839599 in Gr 4.205, but I don't know if it's still available from GM. (not likely) However, this same spring was used in all PowerGlide transmissions, including passenger car, for at least ten or more model years so finding a used one shouldn't be too difficult. Check with some of the older automatic transmission shops in your area. They'll know what you're looking for.

The next possible cause of rough downshift in a PowerGlide is the fact that the original modulators, and all new Delco modulators of that era, were adjustable. The problem is, no one knew about the procedure, or bothered to compare the old with the new for spring tension and make the necessary adjustment if they did know about it. The results were either a rough "klunk" on downshift or a sliding sloppy downshift. I don't remember the exact procedure for returning a new modulator to specs if the original is no longer available for comparrison.

I don't know if all current replacement modulators have the adjustment feature but I would guess probably not. Most likely these newer designs are set to some "middle of the road" spring tension setting.

One more cause of a rough downshift in a PG is the adjustment of the T.V. control linkage, the rod that connects to the carburetor. If this adjustment is incorrect, it will make the 2-1 shift slightly overspeed, then suddenly bang back into low gear when coming to a stop. However, this adjustment should be made after the modulator spring is added and the correct adjustment is made to the modulator. Hope this helps.

[Robert S.]

Re: 62-66 aluminum powerglide

I think this might be the guy your thinking of...http://www.autotran.us/index.html

[Rick C.]

Re: 62-66 aluminum powerglide

Ray, Maybe Bob Sloan at Sloan's Racing Transmissions in Normal, Il can help. John Mattson gave me his name. He (Sloan) has been involved with the Powerglide since it was introduced in 1962. His son Jim is pretty knowledgeable, too. Their number is 309-452-7397.

[Dave S.]

Re: 62-66 aluminum powerglide

Ray,
The fellows name is David Edwards from Needham, Mass. He's about 10 miles from you. His ads are in the Driveline every month.

[Joel A.]

Re: 62-66 aluminum powerglide

Most all aftermarket modulators are adjustable. You can use a small pocket screwdriver to do this. Screwing the screw in increases pressure, and makes the shift later. Screwing it out decreases pressure, and it will shift earlier, and softer. The shifts, up and down are controlled by the TV valve, the modulator, and the governor. Any of these components can create a "harsh" downshift if they are no functioning properly.
While installing a spring on the modulator valve may help soften the coasting downshift, I think the best place to start would be with the TV linkage from the carb, down to the trans. If there is any binding in the linkage, it can cause the TV pressure to remain higher than it should be, and cause a harsh coastdown.

[ray anthony]

Thanks 62-66 Aluminum Powerglide

My thanks to all who responded to my problem. I will be contactng the sources and performing the adjustments mentioned. You have all been a great help, thank you