I had an earlier thread about an idle problem that turned into an overdrive problem so let me start a new thread to make it easier on those who need to search for this issue in the future.

Car - 1991 240 with about 260K on it, automatic transmission
Problem - car will not shift into overdrive.

What I've done so far - 1) checked relay behind center console. clicks on and off as you push the OD button.
2) light comes on instrument cluster
3) wiring looks good underneath
4) and here's where it gets interesting - I had the ignition to the on position where all the power items worked, but engine still off. I went underneath the car while someone else toggles the OD on and off and I could hear nothing underneath the car. On top of the solenoid is a wire harness and it looks okay, and there is one yellow wire that clips on the top of the solenoid. As I removed the wire from the solenoid I could here a definite clicking sound coming from somewhere in the transmission. Each time I touched the wire to where it was supposed to go it clicked. But fired the car up, drove around and still no 4th gear.

Maybe this will help those much smarter than me help me narrow down the problem. I am within a few clicks away of ordering the overdrive bypass kit.

 

so...it sounds like the wire on top of the solenoid is loose. Why not fix it?

 

actually, after some time researching I figured out that what I thought was the solenoid was not the solenoid, I was looking on the driver's side towards the front of the transmission, and it was a black cylinder that said "bosch" on the side once I got up close and personal with it. It was also visible from up top through the engine bay - don't know what it was, but it wasn't the solenoid.

I found a pretty good picture of what I am looking for now and where it is so I should be able to re-inspect the wires tomorrow. It's storming like crazy now and the rain is coming down in buckets.

Each day I attempt to tune up or recondition this car is a day I feel less and less intelligent...

 

installed the OD bypass plate from ipd today. Question for those who have also installed it - what do you do with the wire that hangs down and clipped into the solenoid harness? Are you leaving it there? Cutting it? I'm not sure what to do with it and don't know if it will cause problems just hanging there.

 

I was just about to suggest the solenoid bypass plate! Too bad they charge so much money for something that costs pennies to make.

 

Fourth gear works great! It shifts smooth.

For now I've just left the wire hanging down, should I do anything about it?

I agree with the price thing, it is probably cost $2.00 tops to manufacture, but they have the market pretty much cornered on this one so until someone comes up with something else...

 

I'd leave it on, personally. You never know if you'll need it for some reason. Just put it up out of the way. Doesn't it come back along the transmission oil plate? Leave the wire in the wire hooks hanging down from the transmission oil plate bolts. There should be at least one.

 

I was just thinking that in the od position, the transmission simply shifts into overdrive when it needs too right? So why not block the transmission in that position all the time.
Is this what the overdrive bypass plate does?

 

Yes, that is exactly what the OD bypass plate does. I installed it on my 92 940GL.