Weird auto transmission problem

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crav4speed
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Weird auto transmission problem

Post by crav4speed »

Hello all!

I'm new to the forum and what a sucky post to say hello with but I just bought an 88 635csi and the auto transmission started acting up :( The previous owner said they had rebuilt the tranny a few years ago.

The car shifts into gear and drives but then it will just stop shifting as if it's in neutral. It will be in "D" but the engine will just rev and the car won't move. The only way for the car to move is to shut it off and restart it. Took it to my local mechanic but he couldn't find any leaks or anything out of the ordinary.

What do you guys think it could be? Thanks
crav4speed
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Joined: Fri Sep 04, 2015 8:45 pm
Location: NYC

Post by crav4speed »

So, I've been doing a little research and the majority of this type of issue seems to be with the clutch pack.

I'm ruling out this possibility though because if it was a clutch pack issue, reverse would work. In my case, neither forward nor reverse gears work.

Is there something else I'm missing?
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Brucey
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Post by Brucey »

I would inspect the flex plate and the propshaft etc to see that it is still in one piece; something might be broken.

I would also check to see that the gear lever is correctly adjusted where it goes into the gearbox.

Losing all drive is a bit unusual to say the least. Can you still select 'P'?

Is the oil level OK?

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
crav4speed
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Location: NYC

Post by crav4speed »

Brucey wrote:I would inspect the flex plate and the propshaft etc to see that it is still in one piece; something might be broken.

I would also check to see that the gear lever is correctly adjusted where it goes into the gearbox.

Losing all drive is a bit unusual to say the least. Can you still select 'P'?

Is the oil level OK?

cheers
Hey Brucey! Thanks for responding.

Park is still selectable and the transmission will lock when selected. My indy mechanic put it on a lift and everything looked fine from under the car. He also checked the oil level and it was fine. I'm just really hoping I don't have to drop the transmission.

The issue that has me stumped is that when the engine is shut off and then started again, it will drive but then stop after a few minutes. Before it happens, I can hear a hissing sound as if pressure is being lost somewhere and the car becomes sluggish.

It has been extremely hot and humid here in New York the past few days, so I'm wondering if the hot weather has something to do with it. Could it just be the transmission and oil overheating causing the clutch plates to lose friction? Would a transmission oil change hurt?
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Brucey
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Post by Brucey »

a hissing sound? That is odd.

Stupid question; you are dipping the oil level when the oil is fully hot, with the engine running, right? That is the way it should be done.

It just might be that the filter on the bottom of the tranny is

a) blocked and/or

b) loose or missing its seal.

This would (esp if the oil level is actually a bit low) result in the gearbox losing oil pressure once it has been running for a few minutes. The hissing sound might be the pump sucking on air?

I think that the gearbox can do all kinds of weird things if there is no oil pressure. Somewhere online there is a manual for these gearboxes which may help you to diagnose the fault better.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
crav4speed
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Location: NYC

Post by crav4speed »

Brucey wrote:a hissing sound? That is odd.

Stupid question; you are dipping the oil level when the oil is fully hot, with the engine running, right? That is the way it should be done.

It just might be that the filter on the bottom of the tranny is

a) blocked and/or

b) loose or missing its seal.

This would (esp if the oil level is actually a bit low) result in the gearbox losing oil pressure once it has been running for a few minutes. The hissing sound might be the pump sucking on air?

I think that the gearbox can do all kinds of weird things if there is no oil pressure. Somewhere online there is a manual for these gearboxes which may help you to diagnose the fault better.

cheers
Yes, oil level was checked with the engine hot. I'm going to try a full tranny oil and filter change and see if that solves the problem. More searching pulled up this thread:

viewtopic.php?t=9817&highlight=automatic+transmission

Hopefully the oil and filter change solves it. I'll update this thread after. Thanks for all your help Brucey!
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Ralph in Socal
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Post by Ralph in Socal »

Doesn't the 88/89 system utilize a trans control unit? I'm not that familiar with the later models.


Ralph
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Brucey
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Post by Brucey »

crav4speed wrote:
Yes, oil level was checked with the engine hot.....
with the engine running....? That is how it is meant to be done, with the engine off gives a false reading.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Pod
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Post by Pod »

Brucey wrote:
crav4speed wrote:
Yes, oil level was checked with the engine hot.....
with the engine running....? That is how it is meant to be done, with the engine off gives a false reading.

cheers

..........and run it through the gears first :wink:
GregB86

Re: Weird auto transmission problem

Post by GregB86 »

crav4speed wrote:Hello all!

I'm new to the forum and what a sucky post to say hello with but I just bought an 88 635csi and the auto transmission started acting up :( The previous owner said they had rebuilt the tranny a few years ago.

The car shifts into gear and drives but then it will just stop shifting as if it's in neutral. It will be in "D" but the engine will just rev and the car won't move. The only way for the car to move is to shut it off and restart it. Took it to my local mechanic but he couldn't find any leaks or anything out of the ordinary.

What do you guys think it could be? Thanks
I have a very similar problem. My 1989 635csi slips out of gear every now and then but only in 'E' if I put it in 'S' the problem never occurs. Only problem with that is that is of course I dont get top gear.

Greg
Pjay1918
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Re: Weird auto transmission problem

Post by Pjay1918 »

Sorry to resurrect a dead thread but did you ever figure out what was causing your problem? My car has the exact same symptoms you described and I haven’t had any luck finding a solution.
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