I have a 99 ram 2500, 24 valve desiel, auto trans. At 45 mph the whole vehicle surges, acting like it is jumping in and out of overdrive. it does this usually when cruising, not when underload or accelerting rapidly up to highway speed. It only last untill the truck hits 52-55 mph then runs normally, and does not ever do this when the overdrive is off. I have never worked on an auto trans so am at a loss at to what could be causing me this problem.

 

I have know idea. I have a friend that built my trans in my truck i can ask him. but he is hard to get ahold of may take me a few days.

 

hey, check battery cables for corrosion and clean if necessary... if the batteries are old or sulfated they will also cause this condition. the alternator charging is sending spikes to the electrical system causing the computer to see these spikes in the tps volts.... check those first... you could have a failed tps but not alot seen here.... if you keep driving it like this the torque convertor will fail seeing it is the lockup your feeling not going inand out of OD

 

Hmm wouldnt the spikes come from the alternator at all speeds instead of exactly at 45 mph? I will check the cables and Batteries just to make sure tho.

 

At 45 mph is when your trans is trying to lock the torque converter. That's why you notice it only at that speed. The spikes are not bad enough to cause the locking/un-locking when you are traveling faster or slower than the lock up speed. The problem you are experiencing is fairly common. The speed at which you describe your problem is a dead give away. 99% of the time cleaning ALL major electrical grounds will fix the problem as long as it is not the batteries themselves.

 

I have talked to my trans guy. He said the same thing as BrianSudokhoi02.