1990 Lumina Euro 3.1 Overdrive Automatic Transmission Problem

[luminacrazy]

The dashboard speedometer was showing the incorrect miles per hour but the transmission shifted fine, so I recently replaced the Speed Sensor located on passager side of the transmission case to fix this problem. While removing the part I accidently damaged the end of the wire lead going to another sensor on the lower passanger side of the engine block.

Now after replacing the speed sensor and patching the damaged lead going to the unidentified sensor the speedometer reads zero miles per hour at any speed and the transmission will not shift out of 1st gear!

Could anyone confirm that this adjacent wire lead goes to something called the shift sensor and that this damaged wire lead end could be the cause of this sudden shifting problem.

[luminacrazy]

Come on guys, are there no GM service techs out there that can help solve this shifting issue. It is either the new sensor or the broken lead to the other sensor which I am having trouble identifying. I verified with the GM dealer that I had the correct part number. Also the car is stuck in 2nd gear instead of 1st as I said in my initial post.

Please Help!

[sad-lumina-owner]

Originally Posted by luminacrazy

Come on guys, are there no GM service techs out there that can help solve this shifting issue. It is either the new sensor or the broken lead to the other sensor which I am having trouble identifying. I verified with the GM dealer that I had the correct part number. Also the car is stuck in 2nd gear instead of 1st as I said in my initial post.

Please Help!

ouch sounds VERy inconvenient.

I will look in my Haynes manual for some clues... maybe there is a fix, like shorting the sensor and just bypassing the thing.

[maxwedge]

No speedo reading no up shift, the trans is in 2cnd default, now what wire to what sensor did you " damage", usually a non related wire would not affect the speedo. Should be a purple and yellow wire to the speed sensor, confirm all those connections and your installation.

[luminacrazy]

To recap my problem, I recently replaced the speed sensor on the 4 speed transmission because the vehicle was showing an inaccurate miles per hour, however the transmission appeared to otherwise shift correctly.

I went to a GM Dealer that I sometimes use for service on my late model vehicle and I got a GM service tech to give me some clues to the shifting problem. He said that under the shift sensor is something called a "Reluctor" which looks like a gear mounted on a rod with a vinyl gear on the other end which turns at the speed of the vehicle.

When operating correctly the reluctor turns with the vehicle transmission speed and the sensor picks up the speed of the vehicle through the turning gear teeth passing by the speed sensor. Apparently on high milage vehicles the vinyl gear on the drive end wears out, he called "Apple Coring" which results in the vehile not showing any speed on the speedometer, and the vehicle being stuck in 2nd gear. He said that I most likley damaged a lead going to a knock sensor, and like the genleman that replied said, it most likley is not causing the shifting issue.

Mr Goodwrench suggested that I remove the Reluctor and see if this vinyl gear is worn out and replace it if it has apple coring. He said that GM service manuals are very bad about showing wiring diagrams and that I should go to a junk yard and get a wire lead end for that knock sensor that I damaged. I suspect he is correct because the car has over 333,000 miles with the origional transmission and engine.

Also that sensor that I purchased from Autozone may have hung up the reluctor from turning properly and if the reluctor did not have apple coring at the time it mostly likley will have it now from the tight fit of the bad part.

The problem with my vehicle and the "Reluctor" is probably why GM decided to change the speed sensor on the 1991 Lumina.