W124 300TE Does Not Upshift - PeachParts Mercedes-Benz Forum

Dave804 · #1 09-17-2010, 10:10 PM

Hey Guys,
I hate to be the noob and start off with asking questions. But, I've got limited tinkering time because of work and want to make sure I'm looking at the right places for my issue. Car is an 8/88 300te automatic. Mileage reads 208k on a dead odo. Based on service it has about 212k. Car runs well, got it for $1300 and am loving it so far.

The neutral safety switch is out. The coolant gauge occasionally decides not work and there is a surge at idle. I believe they are all related an am waiting on a new OVP to come in Monday. The idle surge is between 1-2k when the car is first started and coming to a stop. Regular idle is about 500.

The transmission will not upshift under regular acceleration. Driving on the highway it continues to rise in speed until engine speed is about 5k. A quick blip of the throttle causes it to upshift so that engine speeds are normal (say 3500 and below). Then after a time it continues to rise until you have to repeat the process. Once, only once it has slipped into neutral. What I believe to be neutral. I was going 70 and coasted off the gas for a prius. When I got back on the throttle it revved freely and went nowhere. Once again with a clip it went to the correct gear. I have no delay in engagement with the selector, no hard shifts, noise, smells, etc. The fluid level was not at max but very close and had no burnt smell.

I believe (in order) these are the best to check?
-Plastic linkage bushings
-Kickdown switch
-TV cable
-Fluid and filter flush
-Fried tranny? Haha.

I appreciate the help guys. Y'all come highly recommend. Its Dave in Richmond, Virginia by the way.

david s poole · #2 09-18-2010, 10:42 AM

dave read the thread on christines car about trannie.it is current.i explain how to clean out the filter for the govenor.i think that may be your prob.

Dave804 · #3 09-18-2010, 06:35 PM

Hey David, thanks for the reply. I read the thread, I like the thoughts of being able to fix this without removing the tranny haha. I have a shop I'll have to go to tomorrow for level ground to drop the rear of the tranny.

Further info for troubleshooting:
This morning during my drive to work was ~63 degrees. The car drove like a dream. Even floored it from 50-100 trying to create symptoms and couldn't get anything.
At lunch it was about 80. Car had the surging idle but drove and shifted fine.
Coming home temp was the same, car was still surging but driving fine. Once i floored it and hit the kickdown switch the trans started to act up.

I'm leaning (maybe hoping) towards a combination of several small problems.

daddi · #4 09-18-2010, 06:55 PM

Check the kickdown switch under the gas pedal, it might be stuck on.

Dave804 · #5 09-26-2010, 10:58 PM

Wanted to give thanks to David, Christine, and daddi.

For anyone that comes across this thread searching, for me it was the kickdown switch. Took the switch off, sprayed some contact cleaner in/around it as best I could and pressed it by hand a few dozen times. Since then I've driven the car about a week (~400 miles) in all temps, speeds, distances etc and had no problems. I think the biggest key to if you're doing your own diagnostics was that it wasn't slow to upshift, it simply didn't until you hit the switch.