Powerglide no Reverse - Impala Tech
Transmission & Driveline Transmissions & Differentials

 
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post #1 of 5 (permalink) Old 11-03-2018, 03:20 AM Thread Starter
 
 
Join Date: Oct 2017
Location: Vancouver, WA
Posts: 19
 
Powerglide no Reverse

Like the title says. Shifting into reverse is like shifting into neutral. Previous owner indicated that it had been that way for some time; I want to diagnose and fix it. 1966, aluminum pg, rear pump. I've already checked the fluid level many times, even slightly overfilling it to no avail.

One thing I read somewhere is that the fluid port that controls the reverse clutch can become blocked with debris over time. On an off chance, I tried some Seafoam trans-tune, which didn't fix the problem. Also read that sometimes rebuilders will install the gasket for a later pg with no rear pump, blocking off the fluid port. Don't know if the trans has ever been rebuilt, but I doubt it.

Checking the fluid port would I believe require me to drop the transmission, somewhat difficult given that I don't have access to a lift. If I'm going to do that job, I want to be sure that it will fix the problem. Does anyone have experience with this problem? Any leads on things I might check? I don't have the money for a new transmission right now, although that's my eventual goal.

1966 Impala 4-door Sedan
283 V8, 2 speed Powerglide Automatic
Black.
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post #2 of 5 (permalink) Old 11-03-2018, 11:24 AM
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Join Date: Jan 2006
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It's broke. Pull it and rebuild it if you really want a broken TH350.

TH350 was designed to replace the PG. Bolts right in no fuss and you get a first gear that offers better acceleration, rather than taking off in second all the time the way the PG works.

It was the annual bloat of the big cars that created the need for the TH350 as people had TH400 envy of those cars that had one and they didn't. Of course cars with a TH400 accelerated better because in addition to an extra gear TH400 equipped cars had more powerful motors.

Big Dave
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post #3 of 5 (permalink) Old 11-04-2018, 02:08 AM Thread Starter
 
 
Join Date: Oct 2017
Location: Vancouver, WA
Posts: 19
 
Yes, my plan is eventual to upgrade to a four speed, however, I don't have the money right now to buy a transmission. In the meantime, I still have no reverse. Any ideas as to what a fix might be?

1966 Impala 4-door Sedan
283 V8, 2 speed Powerglide Automatic
Black.
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post #4 of 5 (permalink) Old 11-04-2018, 09:05 AM
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The clutches are made of paper. Once the paper is shredded that is it. You can put a fork in it or always park on an incline to get out of where you parked, or park by pulling through a parking space so you can drive out of it.

Run a tranny low on oil and the clutches and bands are destroyed; as the paper shreds. Run the tyranny without the paper clutches and you are running steel on steel which burns and gauls the bare metal parts requiring replacement drums and new steels between the clutch packs (those don't come in a kit you get them by salvaging used parts out of earlier projects).

Because the plastic seals in these transmissions were some of the earliest plastics ever invented (like was said in the movie "The Graduate") plastics were a developing industry in the sixties. These early plastic seals dry out and shrank if not covered in ATF all of the time (and even then they leaked a drop or two constantly).

Once the seals are dried out they won't hold oil in the tranny, so it runs out as fast as you pour it in. Takes a while to get them to stop leaking which is why tranny products like "Stop Leak" was made as a repair tool. "Stop Leak" is a chemical that softens the plastic and causes the plastic to expand. This stops the leak temporarily, but also causes the seals to wear out rapidly. It is a trick that was used by used car lots to get a car sold with no warranty that was other wise undrivable.

Big Dave

Last edited by Big Dave; 11-05-2018 at 10:44 AM. Reason: Fix gram Mar erors
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post #5 of 5 (permalink) Old 11-05-2018, 09:00 AM
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Join Date: Jan 2018
Location: Coopersville, MI
Posts: 269
 
The only way you are going to get reverse back is to remove the transmission and rebuild it. You may be able to find a good used TH350 for a couple hundred bucks that would get you by. Just be happy your not a 63 impala as the TH350 swap is a little more labor and part intensive as the floor shifter is bolted to the tranny.
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