Foz

The automatic transmission on my '87 seemed to leak a lot of fluid onto my garage floor over the past few years (maybe a quart). So I took it in today for an A/C recharge and we put it up on the lift to see where the leak was coming from. Long story short, it looks like the pan gasket.

Here is the weird part - I expected the reservoir to be bone dry due to all the fluid leakage over the past two years. But instead it was full to the brim. My question is: With the car turned off, is the reservoir supposed to be completely full? Or is it that with the car turned off, the reservoir level is completely irrelevant, and you have to have the car running to make any sense of the transmission fluid level? Or is it that the mysterious check valve that has been mentioned is broken and allowing fluid to be siphoned back into the reservoir and/or out the vent hole?

Any ideas/theories will be appreciated. I went back through tons of transmission leak posts and pasted all the interesting comments into a text file, but the transmission is still a strange beast to me.

928porschepatrick

Hope this will help you

Foz

Thanks, I saw that diagram from the service manual, but that is the "right way" of doing things (which I'll do after replacing the pan gasket). I was more looking for a "quick and easy" answer (I know, I know, there is no such thing - But I can always hope).

The thing I am really curious about is the full reservoir. After thinking about it last night, I guess that it's possible that the PO overfilled the system and that's why there was a bunch of leakage onto the ground.

But the basic question that I'd really like to know is: Have any of you, when the car is on the lift, or jacked up level had the reservoir be full (to the cap) with the car turned off?

Speedtoys

The level will be OVER the cap, with the car turned off. Always...unless its VERY empty.

Thats why you check the full level with the car running. Many quarts of fluid get pumped up into the system and cooler at that time.

Foz

Cool, that makes sense. Thanks for the info!

Foz

2-1/2 quarts low.

I am the lowest of the low... I am a Shark torturer.

Podguy

There is an overflow button on the top of the transmission. Perhaps someone at one time seeing the oil on the floor added more fluid than needed. How does the transmission run now? Has it blown off enough fluid to be at the right level.

On my mercedes when heading to the high country the transmission pissed oil. When we got down to sea level things were great and it did not need any oil. Very strange but I have no idea where the extra oil came from. These transmission are full of vodoo. You should change the filter and pan gasket and drain the torque converter if it has been a while.

Foz

Sorry, I wasn't clear. Speedtoys was exactly right - The fluid was WAY low even though the reservoir was full with the car not running. Once I had the car jacked up and started it, the fluid level went way down. I added a quart, and it was still way down. So I added another quart and it was still below the min (hot) mark with the tranny hot.

The reason I knew something was wrong (other than the pink stains on the garage floor) was that I went over an overpass today and when the car was at a 15 degree angle, it was stuck in first gear until I pulled over and shut the car off for two minutes (to either de-foam the ATF, or allow it to pool back at the bottom of the tranny - don't know which).

Going to do that next week - Ordering the parts tonight.

WallyP

Time to get a pan gasket, filter and ten quarts of Dexron VI.

You can disconnect or cut (!) a transmission cooler line, let the engine idle until fluid stops coming out. Add as much fluid as you got out, let idle until fluid stops coming out. Reconnect line, drop pan, change filter, straighten pan flanges, replace gasket, properly torquing fasteners. Let engine idle, fill to upper mark.

Foz

Dexron 6??? Wow, Wally, I didn't realize that you'd installed a Flux Capacitor on your 928! Maybe you could pick me up a case next time you're in 2030.

But seriously, thanks for the tips - I hadn't started researching the fluid swap procedure yet. I'm planning on doing the "126 277 09 32" and "722 993 001 00" spring swaps while I'm in there, as well as the crush rings for the plugs. Anything else I should do? I think I'll drain the torque converter while I'm at it.

WallyP

Dexron VI was released in 2005, and is now the only GM-recognized version. All other Dexron licenses have been canceled. There are older versions still being sold, but they are no longer recognized, tested or controlled by GM.

GM says that the specs for Dexron VI are much tighter than for prior versions, and according to them, any conforming product is equal to any other. With that in mind, the cheapest VI that I have found is Walmart's house brand.

The reason for the procedure I mentioned is so all of the old fluid is removed, including the converter, the cooler and all lines. That being said, the 928 does have a drain plug on the converter. If you turn the crank to TDC, the plug will be accessible on the bottom of the converter.

Foz

Oops. Joke fell flat - I didn't realize they skipped straight from Dexron 3 to Dexron 6. I thought you had mistyped Dexron 4.

So much for trying to stump the master...