No reverse after fluid change

[falloutboy]

Hi folks,
well I finally done my overdue transmission fluid change. And after restarting and initial check, all was fine.
Wanted to back out the garage for a short test drive, and heard some rumble and plopping.
Shifted through all gears again, and didn't hear anything anymore. Went for the test drive an all was fine and good.

Now, 2 short drives later, I tried to backup the incline of my driveway and - well - I kinda don't have reverse and the car just rolled down again.
I feel it shifting but after the little jiggle I can just rev it like 5k before it even thinks about moving.

The changed fluid was not burned or smelly, despite having some brown/blackish varnish in the pan, but nothing else that looked suspicious.

Any ideas what could've gone wrong?
Overfill? Underfill (which I doubt thanks to the check plug) Solenoid? or did I sheer something off?
Like the flanges on one of the sun-drives

Got about 250 000 km on it, and never had any issues or strange behavior of it. Shifted soft but definite for years now.

Any hints and ideas how to proceed and have it running again till after the holidays?

[zzyzzx]

That sounds like low fluid to me (actually more like low transmission oil pressure caused by low transmission fluid level). When you checked the transmission fluid level it via the overflow hole was the car warmed up or cold? Did you go through all gears before doing the hole overflow? Was the car level when you did the dole overflow? Exactly what replacement transmission fluid did you use? Did you drain and refill the transmission or do some sort of flush?

If the fluid level is correct and fluid type is correct, I would be looking to boost the transmission oil pressure a little. I am not sure how one does that on an Alero, but on my 1995 Escort, I can do this by adjusting a cable. I have 232000 miles (that's 374000 km to you) on that original 1995 automatic transmission. On a newer car there are ways of boosting transmission oil pressure with electronics (usually just resistors). In my opinion, when an automatic transmission gets old, it sometimes needs a small increase in transmission oil pressure, or just needs transmission oil pressure restored to what it should be (the old cable style systems the cable can stretch, leading to low transmission oil pressure). You use a regular oil pressure gauge with different fittings to check transmission oil pressure, you just need to know what the specifications for transmission oil pressure are and exactly which port on the transmission to connect the gauge to. This information should be in the factory service manual.

I am assuming an automatic transmission.

[falloutboy]

Originally Posted by zzyzzx

That sounds like low fluid to me (actually more like low transmission oil pressure caused by low transmission fluid level). When you checked the transmission fluid level it via the overflow hole was the car warmed up or cold?

Of course, warm

Did you go through all gears before doing the hole overflow?

yes, but this was not the time I heard the growling and rumbling. This I heard after I got he car back on the wheels and shifted into reverse for backing out up the driveway.

Was the car level when you did the dole overflow?

as much as possible, so yes it was level

Exactly what replacement transmission fluid did you use?

Liqui Moly Dexron III - H, almost 7,5Liters

Did you drain and refill the transmission or do some sort of flush?

just a plain drain and refill with new gasket and filter. Nothing fancy.

[zzyzzx]

I forgot to ask if the car was running when you did the hole overflow test?

Are you sure that the lever mechanism between the shifter and the transmission is working?

I mean page 7-168 of the 1999 Factory Service Manual lists 25 things to check for no reverse or slips in reverse.


So, of the things listed as one of the causes, low fluid and low line pressure are the most likely given what you did. It's always possible that the new filter is somehow clogged.

[zzyzzx]

This page from the Factory Serviee manual might also be helpful:


As you can see, things like an improperly installed transmission oil filter, or what you Germans would call a very modest replacement transmission oil filter could cause the problems you are having. Plus there are more things to check on that list.

[falloutboy]

Hi,
all is good all is fine now.
After you hint with the line pressure and a remark on a German Forum about the sound of a shattering brake band, I assumed that somehow 7.5L weren't enough.

So I opened the check plug while the car was cold and off, and nothing - no fluid.
After some fiddling around, I ended up needing 11.5L for this oil change.
In my catchcan there roughly 7.5L.
I have no frigging clue why or where I needed all this additional oil.

Took a long testdrive tonight, and all shift points are correct and shifting is like usual, no slipping, no harsh shifts, short, firm.

Any idea about why I needed 11.5L this time?

[zzyzzx]

You must have been low on transmission fluid before the procedure. Yes, it is possible to run a transmission low on fluid for quite some time (years!) and never know it. 11.5L is almost the total capacity!



Note: Bottom pan removal listed about is just that. It's the fluid you get out when you remove the bottom pan. You get more when you remove the filter also.

[paul ron]

this may be a stupid question but....

how much fluid did you drain into your catch pan?

shouldn't it be the same you'll needed to replace it with new?

mmmmmm

[zzyzzx]

Originally Posted by paul ron

shouldn't it be the same you'll needed to replace it with new?

Yes, but if you were low before you drained it, then you will need to add more than you took out.

[sleepyalero]

Did you pull the check plug after filling, car in Neutral, on level ground with the fluid hot?

[falloutboy]

I drained approx. 7,5L - although it is less, as my catchpan is half a keg and not something square.

Yes, I had the plug open while filling from top, and had the car running in drive. so now after having added 11,5 L it shifts and drives fine.

interestingly as I filled it with about 12,5L it was shiftig really hard and slammed the gears in like crazy.
So I let it drain itself down to ~ 11 again, and all seems fine now.

Really strange. but thank god I don't need to pull the trans.

[zzyzzx]

Originally Posted by falloutboy

interestingly as I filled it with about 12,5L it was shiftig really hard and slammed the gears in like crazy.

That is a symptom of too high transmission oil pressure, which is what happens when fluid level is too high.