My 1990 740 Turbo Wagon (auto trans, 165K miles)recently started exhibiting intermittent problems engaging in various gears. My son first noticed this shifting into reverse and the car behaved as if it was in neutral.

Further examination suggests that this problem only occurs when the car is warm, i.e. after it has been driven 20-40 minutes. After which time, shifting from Drive into Reverse pretty reliably reproduces the symptoms of the car behaving as if it were in Neutral -- can rev engine without drive train engaged. Furthermore, if the gear selector is put into the Neutral position, the car behaves as if it were in Drive -- car will creep forward.

I've noticed that I can pretty reliably get the transmission back into proper alignment with what the gear selector indicates by shifting into 1st, and then shifting into Neutral or Reverse. Shifting into Park when misbehaving does not clear the problem.

I've also noticed that the problem persists after putting the transmission (at least gear selector) into Park,shutting off the engine, and a short time later restarting it.

I took the car to my independent repair shop and their service advisor witnessed the behavior in their driveway but the service techs were unable to reproduce it later in the service bays -- this was before I diagnosed the problem as requiring substantial driving time as a prereq. They claim that the linkage is properly adjusted. Their suggestion was to pull the bottom cover off the transmission (~$220) and inspect for metal debris. I was reluctant at the time to go on a fishing expedition with them as they could not identify probable causes -- other than it may need a new transmission. I replaced the transmission on the car 2.5 years and less than 20K miles ago and I am not eager to dump another $2K into the car without pretty good rationale for doing so.

Does anyone have ideas as to what might cause this type of behaviour and whether there are fixes short of replacing the trans?

Thanks,

 

I'd get under there and check the linkages for myself, often the nylong bushing wear out , mine are all missing right now and shifting (auto) is sloppy.

Is there any slop in the shifter itself or is it tight.?

Pulling the bottom cover off the tranny is very simple, get a gasket beforehand.
Theres a filter in there you can check.
Something doesn't sound right if its eating tranny's, unless the replacement was NG too.
Heres the FAQ
http://www.brickboard.com/FAQ/700-90...issionAuto.htm

 

the linkage makes sense because shifter is sloppy,but would that make trans not to shift only to park.Thank you could you direct me in first finding auto trans cover and what parts I need.THANK YOU, MERRY CHRISTMAS,RICH

 

its on the bottom of the tranny, pretty hard to miss, like a square flat oil pan.

absolute cleanliness is needed if you go in there. critical to clean all grime and grit off the outside of the tranny around the pan before removing it. inside the pan, there's a stack of labyrinth maze-like hydraulic passages, various valves, and little *****, all have to be totally clean when reassembled, you probably do NOT want to take all that stuff apart unless you REALLY know what you're doing, and have the full transmission service manual at hand.. advisable to take lots of pictures during disassembly to aid in reassembly. on the trannys, the filter is a metal screen, so you really don't need to replace, it, rather, you want to inspect and clean it. as they said you need the pan gasket.

 

Try changing the fluid. If that doesn't help, the tranny is toast. The linkage doesn't seem to the issue if the problem is not present all the time. Slow engagement in reverse is a sure sign of impending failure.