Please help me with a transmission problem.

[tsjazz2002]

I tried this once before but got no response. I really need some of you alls expert advice. My automatic transmission on my 1988 635CSI will not go into overdrive. It shifts up and and down but will not shift into overdrive. The D on the dash board display does not show during this malfunction. It will work every once and a while then the D appears. Its almost like there is something loose somewhere.

Has anyone had this problem? If so how did you resolve.

Thanks

[dm635]

now that my son has an automatic i'm getting familiar with the electronic trans.
one thing to definitely check is a circular plug that plugs into the transmission on the drivers side.some ATF can seep into the connector and cause a variety of problems.the plug has a collar on it that must be rotated before the plug will come off.spray inside the connector with some electronic cleaner and then blow it out with compressed air.there are several solenoids inside the trans and the signal goes thru that connector.
then you have the selector switch at the bottom of the shifter and also a trans ECU.i'd go with my 1st option.

[tsjazz2002]

thanks, ill do it tomorrow and let everyone know how it turns out.

[rcM3]

sooo.... how did it turn out?

[tsjazz2002]

Sorrry i didnt post a reply on the results. The story is still being written.
I tried to clean the connections myself but it really had no effect. I then contacted the previous owner who stated that he had the problem in the past which was fixed with a simple adjustment to the throttle linkage. I took it to a local shop today for some diagnostics. They want me to leave the car with them for a few days while they dig in. I just dont feel easy with it. Next week I'll drop it off and will update the post when I finally find the right answer.

[dm635]

the shifter cable where attatched to the trans is also easily adjusted.the shifter may feel like it popped into the selected gear,but the selector switch could be sending a signal that it's not in drive.the switch is driven by the the shift lever.
the adjustment for the cable is very sensitive and took me several(make that many)attempts.the electronic circuit for the trans is very involved.you will need the ETM(electronic troubleshooting manual)to check all the signals.it would take me all day to type out the procedure.it took a very full day of troubleshooting to check each signal with a digital volt ohm meter.
the ETM has a troubleshooting section that is not available in the Bentley.

[tsjazz2002]

I do believe its something simple. I just dont have the time to chase it down. The funny thing is that I walked in the German Car Center yesterday with a stream of posts from Bimmerforum.com. LOL! He looked at me like I was crazy! LOL! I'm a new owner so I tend to trust those of you who have delt with these issues before over a guy who works on all types of vehicles and may see a 635 a couple of times a year.

I'm droping it off this week to have not only the transmission looked at but to take care of a main seal leak, worn lower control arm and leaky steering box. I'm gonna be homeless when all this is done so I need my car to be in top shape, LOL!

[tsjazz2002]

This update is not really an update. Its more of a "what the hell". Judging from the number of people who have viewed my original post I'm not the only one out there fighting the transmission gremlins. Well I have yet to find the source of my problems. I did take it to a guy here in Savannah but I just didnt get a easy feeling from him. He didnt see to be interested in my explanation but was more than willing to take my transmission apart to look for my problem.

My gut feeling is that it has something to do with my new stereo. Ok stop laughing! Honestly I didnt have any problems until I had my head unit replaced and my speakers rewired. I just think the guy at CCC must have pulled or pushed something out of wack. Sooooooooooooooooooo, soon as we get a break from the 100 degree heat I'm going into the dash.

By the way, those of you looking to upgrade your stereo look no further than Nakamichi for a great stock look. I went with MB Quartz 4" components in the front and Kicker 5 1/4 seperates in the rear. I couldnt be happy with the sound. If you are looking for boom, boom , boom this will not do it but if you like crisp clear music with great detail then you can't go wrong with the configuration. At least it sounds good even if it will not go into overdrive! LOL

[tsjazz2002]

Remarkable story! So many people have viewed my original post so I'm sureyou are all waiting with baited breath for a resolve. Well, well, well! You have to just love the personality of the 6'er. On the way home from work today I was riding along thinking about adding an amp to my stereo system. I reached up under the the center control by the selector switch to see how much room I had to run wires. The pressure from my fingers under the leather caused the car to jump into overdrive. Hmmmmmmmmmmmmm, what the hell. I kept driving and everytime I pulled my hand out the car went back into third. So I removed the ashtray, pulled and pushed on the wiring and low and behold the car stayed in overdrive shifting thru the auto flawlessly. Just like I suspected all along all I had was some loose wiring. The lesson learned here is that before you start spending big money you need to apply the kiss principle (keep it simple stupid).

Thanks for all who weighed in. I hope my experience can help someone else down the line. :redspot

[dm635]

you can easily pinch/stretch the wiring when changing out head units.when i installed a regular DIN Pioneer unit,it would not fit flush and i was very careful with the other wiring behind it.i even had to trim the thick felt covering on top of the fan in order for the unit to fit flush.thanks for updating!!!!
it is impossible to give the correct advice on that type of situation.i gave the problems i had,but someone else jamming a new stereo in there and doing damage to the wiring never crossed my mind.