Hey guys-
New to this whole diesel thing here and was wondering if you could help me. I have a '93 W250 CTD with an auto and am having some shifting issues with it. Now I've already looked back into some older posts and I did find one with someone seeming toi have a problem similar to mine but I don'y know if it was ever fixed or not. What is happening is driving down the road the tranny doesn't want to shift into OD. If it does it only stays for like a second and then kicks back into drive. This happens even without moving the throttle. It gets real annoying to hear the truck screaming like it does. I have serviced the tranny with new filter and fluid and still nothing. It was also doing this before I changed the fluid . I'm not big into auto's so there like a foreign best to me so any help would be appreciated. Thanks.

 

It sounds like you could have a problem with one of three sensors - the throttle position sensor (TPS), the crank sensor (CKP), or the vehicle speed sensor (VSS). If you have no charging system problems, it's not likely to be the CKP. If the speedometer and cruise work right, it's probably not the VSS, so that leaves the TPS. Click on the link for a thread with good info on TPS adjustment and diagnosis. There is also a link in the thread that will take you to a page with more info on repairing your own TPS.

 

wannadiesel forgot the tranny temp sensor, and the "brain" chip (the acronym completely escapes me at the moment).

i have the same truck and had the exact problem you describe. my truck would occasionally (once every week or less) hit OD for a seccond and right back to 3rd. turns out it was a cocktail: one bad VSS, one bad TTS, and one bad "brain" (maybe it's called the ECM?).

point is, it's electrical. more than likely the mechanical parts of your tranny are fine. also, finding a competent trany shop to deal with these electrical problems is next to impossible. take a list with you of things to check TPS, VSS, TTS, and ECM. make sure he/she checks them all as more than one might be bad.


jeremiah

 

Hey guys, thanks for the info. Wannadiesel-I tried the TPS adjustment and it shifts sweet now. I still have minor tweaking to do to it but it's 100% better now. My initial at idle reading was like 1.04 and WOT was somewhere arounf 3.27. I guess both were in spec but tweaking them a bit helped. I think I rought the idle reading down to between 1.01 and 1.02. Just that little bit made a differnce! Like I said it shifts great now and I appreciate the help. I knew one of you guys on here could help me out!