Wife's '91 740 wagon with auto trans won't shift beyond 3rd gear. Starts in 1st, goes into 2nd and 3rd smoothly with no problem, but won't go past 3rd gear. Overdrive on or off makes no difference. No sounds, noises, or any other evidence of transmission failure.

Any ideas?

I really hope this is somthing simple as it has 260K+ miles on it and I'm tired of dumping cash into this bottomless money pit.

Thanks,
Marty

 

Bad over drive switch, relay, or actually in the transmission. I believe the first thing to do is check your electrical connections. If your light still comes on when you engage overdrive that means your relay is working and your overdrive solenoid is still getting power. Because the light and the solenoid are on the same circuit.

If your light is coming on normally that tells me your electrical systems are working and it is something with the solenoid or the overdrive itself. Start checking the small things like kick down cable adjustment and ATF level and condition. Then check your wiring,with the car not running but in the on position put your car in drive and click the OD switch, if you here a click you're relay is working, but your wiring from your relay to your OD might be bad.

 

I had the same problem with my 1988 740 and all i had to do was install the overdrive bypass plate from www.ipdusa.com that costed like 40$. This process will completely bypass the overdrive system and turn your car into a standard 4 speed automatic. There are also ways to grind out the overdrive solenoid with the proper tools for free but id just spend the 40$ on the bypass plate. Oh and i dont see why your 91 740 is a bottomless money pit... alot of cars never see 260k miles.

 

When you say "the overdrive itself" does that mean something in the transmission? I had a 240 whose overdrive (and corrasponding dash light) would kick in and out at will, making my car shift gears randomly. i am nearly certain that this was a bad relay but alas, i blew up my engine before replacing it. Now I have 760 turbo with a similar but different problem, it wont switch into the highest gear (4th, i guess) at all, but the switch on the gear selector and the light function correctly (at least in relation to each other) but nothing happens, stays topped out at 3rd gear. This is my girlfriends car, I drove it home for her when she got it a month ago and overdrive worked fine. She is not sure if this has been happening before today or not. It was confusing to me because I had just replaced the harmonic balancer and took her for a test drive, this is when I noticed the OD problem. My first instinct was "what did I mess up while fixing something else?" but then realized I had not been driving (nor riding) in this car so not sure when the problem started happening. Please help me, she needs to get out of the house and back to work for sooooooooooo many reasons!! I am thinking of getting the solonoid bypass plate but if thats not it, I probably have a big problem here, right?