transmission problem with mercedes 350SDL
 

I was driving my 1990 350SDL and the automatic transmission would not shift from first gear to the higher gears. It seemed to be trying to change gears but it felt like it was slipping and just couldn't do it I checked the transmission fluid and it was full. I was about 70 miles from home and had to have the vehicle towed- since the car could not be driven on the highway and started to overheat at 20 MPH. Is there a possibility that the transmission screen is dirty and needs to be changed - I had this problem with a 300SD and changing the screen solved the problem.

The 350SDL has been given all routine maintenance and has about 120,000 miles on it. This car is just like new and prior to this incident it was just as tight as can be and ran like it was new.

Any suggestions would be appreciated.

thank you,

Marvin Smith

Marvin if you find out whats wrong with your tranny please let me know. I have the same identical problem with a high mileage 1985 500 SEC. I was driving on the highway and the temp gauge started going up as if it was going to overheat. I pulled over and checked the fluids. They looked ok but when I tried to drive off the tranny refused to shift from 1st gear to any higher gears. I had to get it towed. Had the fluids and filter/screen changed and still it wont upshift!!!

Hello All,
Checking transmission pressures is important to diagnosis.

Additionally please read this link

http://www.peachparts.com/shopforum/tech-help/89030-been-here-before-without-camera.html

Yep, the rear pump check valve and spring has caused many governor gears to fail. MB has a kit to eliminate the rear pump and check valve. If you do not have a pressure gauge you easily diagnose the governor by removing its cover and if you can turn the governor by hand, the gear is bad If not the B1 servo has a leak. Other possibilities are 1-2 shift valve or 1-2 feed control valve; valve body.

trans problem
 

it has been my experience that the valve body has died.rebuilt ones available from dealer for less than 500 bucks.make sure that you replace all 10mm bolts in correct place and only use quarter in.socket set (overtightening will warp valve body)it has probably been temp.cycles over time that got you to this point.(body made of aluminium which is not elastic by definition and will shrink)good luck.