Transmission intermitent problems on 95 Turbo

[PerthX]

Ok this is probably far more important than my AC issues so I saved the best for last as it were. I have a 1995 850 Turbo sedan, roughly 225k miles.

Every so often I can feel the transmission not shifting normally let alone smoothly and RPMs running at a higher than normal and of course this is when my check engine light comes on. Usually I pull over and shut off the engine. I have dutifully checked and there are no engine error codes or any sort. Usually I clear the Check Engine light, and when I restart the engine, RPMs and transmission seem back to normal. This "seemed to be happening" on really really hot days, outside temps at 95 and higher.

Now on a relatively cool day, just after I start my car cold the arrow light indicating the car is in a low gear started flashing when put into regular drive, the check engine light went on and of course RPMs were high and transmission just wasn't shifting. Shifting to a low gear did not stop the arrow from flashing.

Did the normal routine as stated above, checked for codes, none, then cleared the check engine light, let it sit 5 min and restarted and the thing seemed 'normal'.

Now I have only had this car for about 7-8k miles. I changed the trans fluid via drain and replace when I first got the car and again 3-4k miles later. In both cases, the cherry red fluid was now a very dark brownish/black. There was no discernible out of the ordinary smell. Now 4k miles since last drain and replace, am thinking about drain and replace again.

Help! Is my transmission about to die on me? What is the problem? Am I wasting my money draining and replacing the fluid? Thanks for any and all help or suggestions.

[jblackburn]

Actually it sounds like the tranmission speed sensor may be bad.

Have you been reading the codes via OBDII or the OBDI ports under the hood? OBDI will clue you into much more information about what it's actually mad at. Try reading A1 next time this happens.

The brown fluid may be old fluid still running through other parts of the transmission that you didn't get before. I would suggest either graduating to an entire pump out and flush of 12 quarts, or doing 1 more drain and fill and then moving to that later. That way, you can get all the old burnt fluid out of there, and you have eased your car into the transition of new fluid already.

[PerthX]

I am pretty sure that the A1 was giving me the 1-1-1 all clear signal. Will make sure next time it happens. Where do I find the transmission speed sensor on the engine? Easy or hard to replace? Anything else you can share about it?

[jblackburn]

It's located just on top of the transmission itself, right below the air intake pipe to the turbo. Wait and see if you get codes to return, but the high RPM shifting, flashing arrow, and check engine light would make that a suspect.

IMG_0028.jpg (85.45 KiB) Viewed 1425 times

Generally a PNP switch will give you transmission ratio incorrect codes, but you could still try rowing the shifter between P and L quickly if it happens again.

Try reading A1, A2, and A5 next time. Maybe there are codes hiding in A5.

[PerthX]

Well my Flashing Arrow and transmission problems have been put to rest. Cleaned up the PNP switch, drained and added a fresh transmission fluid (roughly 4-5 quarts} and everything is working smoothly. And no more error codes or check engine light emanating from this issue.

That PNP switch was so dirty looking, the old dielectric grease so black and thick, I am amazed the car could shift gears at all. We had to file down the copper doohickies a very little. Heck the one spring couldn't even move when we took it apart, it was so gunked up.

Don't believe the guy who posted it only took him 15 min. Took at least an hour just to get the dang thing out of the car before my buddy and I could get to cleaning it. And my buddy is a pro mechanic. Cleaning is much better than wasting $90-160 on a replacement, imo.