EM Powerglide does not shift to drive or low

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NME768
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EM Powerglide does not shift to drive or low

Post by NME768 »

Hello All,
I have an issue with my Powerglide which is quite a head-scratcher. The problem is it won't shift to drive or low but it will shift to neutral and reverse. I can tell because when the hand brake is applied there is an obvious load on the engine. I flushed the transmission and replaced it with new fluid. The band adjustment screw is adjusted by applying 40 in/lbs and backing off by 4 full turns. The fluid was at the full mark on dipstick (checked when warmed up and in neutral) and there are no leaks. The modulator is new and the vacuum line is hooked up to the vacuum balance line between the two intakes. I drained the fluid and it looks clean. I have taken the pan off and verified that the manual valve is adjusted properly and the shift cable is installed correctly, see images. The strainer did appear to have any clogged however there might be some restriction from the valve body indentations caused by the tranny bottoming out, more on this further down. I cannot find anything on the internet showing anyone having the same issues as what I have, and the troubleshooting guide from the 1961 shop manual and Clark's Corvair technical section doesn't contain any issues similar to mine. Upon further inspection, it appears that the transmission bottomed out hard sometime in its life. The oil pan has evidence of being welded up to seal some leaks. Also, there are chips of material cracked off from the large valve body but there there is no obvious breaches in containment. The cracked off residual material was not found at the bottom of the pan but it is possible that they were removed when the pan was repaired. I removed the valve body and took apart all the valves and there is no evidence of binding. The bores of the valve body and pistons do not have any scarring or markings indicating any obstructions. I did not see any metal filings or large particulates during disassembly. I was able to move the low servo piston freely up to 1/8"-3/16".

So after much thought and research, the only thing I can think of is that the bottoming out event could have over-compressed the valve body gasket causing bypassing between the passages. There is also a possibility that hairline cracks could be present in the larger valve body section would reduce the pressure enough to insufficiently release the bands.

The car is:
1962 Corvair 4dr Monza
Powerglide is original and was mated to a 82hp motor
The original mileage is 40,000 miles

So, I ordered a new gasket and another large valve body to replace mine. I just wanted to get everyone's take to see if you have run into a problem like this or have any suggestions.
Attachments
image showing my current configuration as I understand it.
image showing my current configuration as I understand it.
Manual valve in Low is flush with outside housing.
Manual valve in Low is flush with outside housing.
Only visible damage on valve body from transmission bottoming out.
Only visible damage on valve body from transmission bottoming out.
Damage to strainer from transmission bottoming out. No large breaches in strainer.
Damage to strainer from transmission bottoming out. No large breaches in strainer.
Regards,
Frank from Calgary, AB

1962 Corvair Monza, 4dr, 110hp (originally 82hp)

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Re: EM Powerglide does not shift to drive or low

Post by bbodie52 »

Please click on the link below and read through this other thread. I would strongly suggest that you invest some time and view the videos you will find there. The final video does a good job of explaining why changing the old transmission fluid and installing fresh fluid can actually aggrivate the problem and highlight other weaknesses with the internal seals if they are worn or leaky/stiff. Since you just changed the fluid and now have newly discovered problems with shifting, the comments in The Basic Parts of an Automatic Transmission, Part 2 may be applicable here ...

Reverse slow to engage
:link: viewtopic.php?f=55&t=16119
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Image 1966 Corvair Corsa Convertible

joelsplace
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Re: EM Powerglide does not shift to drive or low

Post by joelsplace »

"explaining why changing the old transmission fluid and installing fresh fluid can actually aggravate the problem and highlight other weaknesses with the internal seals if they are worn or leaky/stiff"
That's actually an urban legend/old wives tale/mechanic's tale. I've fixed quite a few transmissions by changing fluid numerous times.
I think the tale got started because people waited to change the fluid until they were having issues and it was too late. New fluid won't fix burned bands/clutches. The trick is if you are changing the fluid to fix an issue take it easy on the transmission and give it time to clean things up. Most transmissions take at least 5 changes to get most of the old fluid out but you'll never get it all.
Would you not change your engine oil if it had been in there too long?
114 Corvairs, 5 Ultravans and counting
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NME768
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Joined: Mon May 07, 2018 6:25 pm
Location: Calgary, AB Canada

Re: EM Powerglide does not shift to drive or low

Post by NME768 »

Thanks Brad for the videos and info. I will take a look. I have been doing a lot of reading including the documentation at corvair.org to see where my issues could occur. To tell you the truth I do not know if this transmission ever worked but the tranny does look original.

Thanks Joel for your input. I have always been curious about that statement with regard to the old fluid. I had my buddy at GM speak to an older transmission mechanic and they said usually a thorough transmission flush fixes this kind of issue with powerglides. They said that, usually, powerglides are bulletproof.

Anyways, I will keep researching otherwise I will wait until the parts come in try it out again. I will also look into the Trans-X.
Regards,
Frank from Calgary, AB

1962 Corvair Monza, 4dr, 110hp (originally 82hp)

64powerglide
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Re: EM Powerglide does not shift to drive or low

Post by 64powerglide »

Do this first.
Attachments
Powerglide.jpg
64Powerglide, Jeff Phillips

Kalamazoo, Mi..

NME768
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Re: EM Powerglide does not shift to drive or low

Post by NME768 »

64powerglide wrote:
Tue May 19, 2020 10:08 pm
Do this first.
Hello Jeff,
I have already confirmed that the throttle is installed and adjusted properly by removing the pan and observing the manual valve at every gear. You can see this in the attached photos where I have inputted labels. Thanks for the suggestion though.
Regards,
Frank from Calgary, AB

1962 Corvair Monza, 4dr, 110hp (originally 82hp)

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Re: EM Powerglide does not shift to drive or low

Post by bbodie52 »

joelsplace wrote: » Tue May 19, 2020 8:24 pm

"explaining why changing the old transmission fluid and installing fresh fluid can actually aggravate the problem and highlight other weaknesses with the internal seals if they are worn or leaky/stiff"
That's actually an urban legend/old wives tale/mechanic's tale. I've fixed quite a few transmissions by changing fluid numerous times...
Image

The Powerglide Diagnosis Guide section "Slow going into both low and reverse" suggests the possibility that "All of the lip seals are hardened. Use TransX". "Clutch seals leak" is also often given as a possibility in several troubleshooting charts. It is also suggested in the troubleshooting chart that using TransX may help to correct a problem with the seals. About 5 minutes into the final video in my other post viewtopic.php?f=55&t=16119 (also shown below) comments on how changing the fluid infrequently in an aging transmission can result in a buildup of foreign material in the old fluid, and that seal contamination, deterioration and hardening may possibly have their deterioration masked somewhat by the older contaminated fluid... only to have the poor seal condition exposed and revealed when the old fluid is flushed out and replaced.

Image




I have not ever subscribed to the belief that an oil additive in either the engine or an automatic transmission will perform miracles in fixing a mechanical internal failure, but I could believe the possibility that a chemical conditioning and cleaning of internal seals may soften and clean them sufficiently to possibly improve the sealing characteristics, which may in turn improve the hydraulic pressure sufficiently to improve the engagement of the clutches and bands that allow the automatic transmission planetary gear sets to function properly. An automatic transmission is a very complex hydraulic device that may begn to malfunction as the bands, clutches, and seals change their performance and function with age and wear. Changing the fluid alone may correct some deficiencies, but may also reveal other problems, such as bad seals causing slow shifting or slippage in the internal friction surfaces. Products like TransX may breathe new life into an aging transmission if it actually softens seals and improves the hydraulic engagement of the internal clutches and bands. If the single action of replacing the transmission fluid reveals/causes a new fault, such as slow/delayed shifting into some gears or transmission slippage when accelerating, perhaps a chemical additive such as TransX may actually improve the seals sufficiently to restore some service life in the transmission, without forcing a transmission overhaul and repair. It may be worth the experiment by trying the additive to see if the seal conditioning and cleaning action solves any problems and possibly gives some additional life to your transmission. The longevity of such a "fix" would be unknown, and fixing such faults may ultimately mandate an overhaul or transmission replacement. But a few dollars to try the oil additive might be worth the experiment.
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Re: EM Powerglide does not shift to drive or low

Post by joelsplace »

"deterioration masked somewhat by the older contaminated fluid... only to have the poor seal condition exposed and revealed when the old fluid is flushed out and replaced."
I'm calling BS on that. Contamination won't make seals work better they will work worse because they have to deal with bits of junk. Old fluid is also broken down and has lower viscosity so it will leak worse than new higher viscosity fluid will. The only thing that I've heard that might make a little sense is the new fluid could loosen up junk that had previously been stuck somewhere harmless and cause problems but I've never seen that happen and I used to rebuild transmissions for a living.
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NME768
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Re: EM Powerglide does not shift to drive or low

Post by NME768 »

joelsplace wrote:
Wed May 20, 2020 6:30 pm
"deterioration masked somewhat by the older contaminated fluid... only to have the poor seal condition exposed and revealed when the old fluid is flushed out and replaced."
I'm calling BS on that. Contamination won't make seals work better they will work worse because they have to deal with bits of junk. Old fluid is also broken down and has lower viscosity so it will leak worse than new higher viscosity fluid will. The only thing that I've heard that might make a little sense is the new fluid could loosen up junk that had previously been stuck somewhere harmless and cause problems but I've never seen that happen and I used to rebuild transmissions for a living.
Joelspace, I was wondering if you could provide advice from your experience. I think it is possible that the change of the fluid could have loosened or removed contaminants from the crevices within the worn out seals since there the new fluid contains strong detergents. Once I put everything back together I probably will put in some TransX as Brad had suggested. I just want to be sure I have exhausted every option before overhauling the tranny if all fails. To think I just put it back in. 😪
Regards,
Frank from Calgary, AB

1962 Corvair Monza, 4dr, 110hp (originally 82hp)

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Re: EM Powerglide does not shift to drive or low

Post by bbodie52 »

:idea: :confused: :typing: More correspondence from the other thread that may be applicable here...
Re: Revese slow to engage
Post by joelsplace » Sun May 17, 2020 7:57 pm

Brad nailed it. 99% chance "hardened, worn or leaky seals" is the problem. It may have more issues since the bad seals will lead to burned clutches.
Unhook the vacuum modulator and plug the vacuum line to the engine and give the Trans-X a try. Disconnecting the modulator will increase the line pressure and compensate for the leaky seals. It might be enough to get you by while the Trans-X does its work.

An easy way to check the shift cable adjustment is slowly move the lever toward drive and note where it engages. Move it slowly toward reverse. It should engage a the same distance from neutral. If it doesn't the adjustment is off.
Post by bbodie52 » Mon May 18, 2020 7:56 pm
albjerryg wrote:
» Mon May 18, 2020 2:46 pm

I will give it a try. Don't you think I would see some fluid if the seals were leaking? Thanks
It is not necessarily the external gaskets and seals that are of concern. Even if the transmission fluid is not leaking out of the transmission, internal leaks and seals that are stiff with age and chemical deposits may not be controlling the fluid internally. An automatic transmission like the Powerglide is like a fluid-based computer (as opposed to electronic) that controls shifting by rerouting fluid through internal passages to perform work by engaging various friction clutches and bands to cause different gear sets to engage and release...

...Hardened or leaking internal seals can interfere with the intended actions in the transmission design. The hope in using transmission fluid seal conditioner is to soften and increase the pliability and effectiveness of the internal seals, so that the "fluid shifting" can function as originally intended. If this fails it may be necessary to overhaul and rebuild the transmission, basically replacing worn seals and clutches and cleaning all of the internal passageways.

The Basic Parts of an Automatic Transmission (Part 2) does a good job of explaining why changing old, dirty, contaminated fluid and replacing it with fresh, clean fluid can actually cause other problems with the internal aging seals to become more pronounced and noticeable. If you are willing to invest some time in watching the videos below, the basic concepts of automatic transmission operation will become easier for you to imagine and visualize.

:pray: :dontknow: The hope is that the TRANSX seal conditioner may recondition the internal seals enough to restore some of the functions needed for proper operation. It may or may not work — but if the effort is successful you may gain some years of operation out of your transmission without having to rebuild or replace it.
Re: Reverse slow to engage
Post by albjerryg » Wed May 20, 2020 4:33 pm

OK I did what you said and right now it look like it is working. Thanks
Re: Reverse slow to engage
Post by bbodie52 » Wed May 20, 2020 9:14 pm

:goodpost:

:dontknow: Did you disconnect the vacuum modulator, add TransX, or both?

I appreciate your update. I don't have a great deal of experience with Powerglide-based Corvairs. My first Corvair (in 1969) was a 1963 Corvair 500 2-door coupe with an automatic Powerglide transmission. I learned to overhaul and rebuild my first Corvair engine with that car, and after discovering an inoperable Powerglide with burned-odor brown-colored transmission fluid, I taught myself to overhaul that transmission as well. But all of the nine Corvairs I have owned since then have had manual 4-speed transmissions, so most of first-hand experience with attempting to correct problems like yours has only been theoretical (until now). Some others have expressed uncertainty and doubt about the effectiveness of using an additive like TransX in a faulty Powerglide. So if draining aging fluid and installing fresh transmission fluid appeared to expose new problems (like slow shifting into REVERSE), and if adding TransX afterward seems to make an improvement, and if that approach proves to be effective, your feedback can be a valuable "lesson learned" that can be helpful to other Corvair/Powerglide owners. Please let us know of your experiences, if TransX was used, of the effect and improvement and if it was immediate, and if performance continued to improve over time. Thank you.
Reverse slow to engage
Unread post by albjerryg » Thu May 21, 2020 8:53 am

Yes I did disconnect the vacuum modulator. and added the trans X.
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Re: EM Powerglide does not shift to drive or low

Post by joelsplace »

I would put in the Tran-x, disconnect the vacuum line to the modulator, plug the open vacuum line to the engine, get the back wheels off the ground and put it in reverse and set the brake. Run the engine until the transmission is hot.
Put it in neutral and let off the brake. At idle shift to low and see if the wheels start turning. If they do that is good. Let it run in low for a minute to get the Trans-X circulated in the low circuit. Go back to neutral, set the brake and shut it off. Let it sit long enough to cool off. Repeat as many times as you have patience for or until things start working correctly. The idea is to get the Trans-X where it needs to be let it soak and then replace it with fresh Trans-X. Of course it won't do any good if hard seals aren't the problem. You don't want to run it much in a gear that isn't working because slipping clutches will burn up quickly.
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Re: EM Powerglide does not shift to drive or low

Post by NME768 »

Thanks guys, I will give it a try. Now I have to just wait for the parts to get in.
Regards,
Frank from Calgary, AB

1962 Corvair Monza, 4dr, 110hp (originally 82hp)

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