I have a 94 Dodge Ram Cummins Turbo Diesel with a 4 speed automatic. When the truck shifts into forth and the RPM is in between 1000 and 1500 the truck starts to buck. It doesnt do it all the time but it does alot. I have to shift it out of 4th gear to get it to stop. Any suggestions on what it might be?

 

Check the tps.

 

Don't run it that low on rpm in that high gear.

 

Describe the buck a bit more, does it go in and out of lockup or in and out of od or does it surge like your giving it more fuel??? A little more description please?? Goodluck,,,Rick

 

It doesnt go in and out of lockup, i usually need to step on the pedal more to get it to stop shaking, its almost like one cylinder isnt burning.

 

Dirty injector?? A bit of water in the fuel? I would start with new fuel filter and go from there. How long has it been since the fuel pre screen has been cleaned or replaced? Goodluck,,Rick

 

Do you have any mods on the truck? I have several (see sig), but mine started to "buck", I think it sounds and acts like a race car with a performance cam, at about 1000 rpm. It started doing this after I put in the injectors and set timing up to 16*. But mine does it in like first gear when I'm just barely giving any throttle. It does sound to me like you are getting into OD too soon. If I leave my lockup switch on, it will buck when I get back on the throttle at under 1400 rpm. So if you have no mods, and the truck is shifting into OD on its own, I think that Injector Jack is probably right with a tps problem.

 

I dont like the truck to shift to early as it is hard on the transmission. Low rpms = low pump pressure. I have adjusted my transmission to extended shifts, by the throttle lever. I have head that the governor can be adjusted to move the stumble in a different rpm. Good luck jimk

 

Thank to everyone for the tips. Ill get right on it!!!

 

My 95 has had this habit since new and I always thought it was the converter or trans. Rebuilt the trans last summer and replace the converter with a DTT and it still can shake your fillings loose if I run no RPM as you are describe. Found out that when I run low revs it is slightly overfueling at that time and I can get high exhaust temps, so I lock out OD in town now.

 

On the '94 auto, there was a pretty "secret" TSB that involved chnaging out the computer. My dealer was very friendly, and the mechanic got them to make the change.

This was early in the production, so for this mechanic, I was a bit of a guinea pig.

 

Mine started doing it with the 4k gov kit. I think thats the problem and PDR says Its a live with it thing.
DM01