Transmission problems -- and compass is related - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-23-2002, 12:20 PM   #1
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Default Transmission problems -- and compass is related

New member here, so go easy <grin>


I have a 94 SSEi with about 120,000 miles on it. No problems until just recently. The transmission started to act funny. It sometimes shifts and sometimes doesn't. Mainly it "forgets" and stays in a lower gear. Othertimes is seems as if it is just slipping (remember the old days when you trashed your Torque Convertor and it took FOREVER to get the thing up to speed?).....

I also get the Service Engine soon light to come on intermittently (scan codes indicate "transmission problems" duh!!! so much for the Poncho dealer)....

And when it is acting funny, the speedometer (and the HUD) both drop to 0 mph.

So far everything points to the tranny itself -- dealer thinks that it is the front inner seal.


BUT:

I think it is one of the computers -- why?? Because whenever the tranny goes mad, the compass stops responding (stays lit and but just doesn't respond to turning) and the engine starts to sound like crap - but not quite failsafe mode. AND every so often, the engine suddenly starts to purr, the speedometer starts to register (as does the HUD), the compass quickly rotates to the proper heading, and the transmission starts to run like a top again.

Then, just as quickly, it looses it again and poof -- no tranny intelligence, rough engine, no speedometer/HUD, and frozen compass.


SO:

without a wiring guide or schematic, what do all of the above have in common? I've done the cursory fuse and relay check, loose cable check and such, but I need some guidance to start really digging into this one -- I'd hate to buy a new tranny and have it STILL fail.

And with the interaction of the compass and engine, I would think this one is unique enough to figure out right away <grin>

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Old 10-23-2002, 12:50 PM   #2
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Man does that ever sound familiar.

Had the same thing happen to my wife'* Montana. Transmission was shifting rough and had me really scared, but the odd thing was the speedometer would start acting funny along with other systems in the car while breaking or turning hard, but the check engine light never came on.

After many hours of testing fuses and looking at the trans, we found the problem. The wire harness going into the computer was damaged and some of the insulation on some of the wires was also damaged making contact with the frame...under hard breaking or turning. I was so glad it was just wiring and not the trans $$$.

Good luck maybe your problem will be the same.
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Old 10-23-2002, 01:49 PM   #3
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Hey, welcome to the forum!

If it'* not what Mario said, or the PCM itself (above the rf passenger footwell), then there'* only one other answer.

Gremlins.

The only part I'm unsure of is whether the compass data actually passes through the pcm.....looking at your symptoms, though, I'd have to say it does.
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Old 10-23-2002, 04:55 PM   #4
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Default Re: Transmission problems -- and compass is related

Quote:
Originally Posted by ecetron
New member here, so go easy <grin>


I have a 94 SSEi with about 120,000 miles on it. No problems until just recently. The transmission started to act funny. It sometimes shifts and sometimes doesn't. Mainly it "forgets" and stays in a lower gear. Othertimes is seems as if it is just slipping (remember the old days when you trashed your Torque Convertor and it took FOREVER to get the thing up to speed?).....

I also get the Service Engine soon light to come on intermittently (scan codes indicate "transmission problems" duh!!! so much for the Poncho dealer)....

And when it is acting funny, the speedometer (and the HUD) both drop to 0 mph.

So far everything points to the tranny itself -- dealer thinks that it is the front inner seal.


BUT:

I think it is one of the computers -- why?? Because whenever the tranny goes mad, the compass stops responding (stays lit and but just doesn't respond to turning) and the engine starts to sound like crap - but not quite failsafe mode. AND every so often, the engine suddenly starts to purr, the speedometer starts to register (as does the HUD), the compass quickly rotates to the proper heading, and the transmission starts to run like a top again.

Then, just as quickly, it looses it again and poof -- no tranny intelligence, rough engine, no speedometer/HUD, and frozen compass.


SO:

without a wiring guide or schematic, what do all of the above have in common? I've done the cursory fuse and relay check, loose cable check and such, but I need some guidance to start really digging into this one -- I'd hate to buy a new tranny and have it STILL fail.

And with the interaction of the compass and engine, I would think this one is unique enough to figure out right away <grin>

-ed cetron
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I think I know what your problem is. I would bet that your speed sensor, or the wiring to it (speed sensor is in the transmission) has gone bad. The compass uses speed signals to help determine direction.

There is a guy that I work with that has an Olds 88 that had exactly those symptoms, and that was the problem.

I hope this helps.
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Old 10-28-2002, 08:49 PM   #5
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Well everyone was close ---

Turns out that the Vacumn Shift Modulator was SHOT... completely gone -- dealer had earlier done work on the tranny cooler and didn't put enough fluid in.. looks like everything overheated and the spring-loaded piston in the VSM went poof.... and then the slipping started and down came the house of cards....

We replaced it and now the car STILL doesn't shift automagically but it will shift perfectly with manual override via the shifter. GM tech tells us that it is because there has been enough slippage in the tranny that the PCM (which appears to be fine) is deciding to start (and keep) the car in 3rd gear...

ARRRGGGHHH -- why you ask is it locked in 3rd??? SO that the customer notices something wrong and comes in to have it serviced <sigh>...

Our best guess is that it needs a full rebuild kit as well as a new valve body (since if the VSM is stuck, no idea what the valve body looks like).... And by the time you do that, you might as well get a completely rebuilt unit..... Anyone seen them cheaper than about $800 or have any better ideas?????


THanks again for all your help so far,

-ed cetron
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