1999 2500 4x4 Quad cab Diesel automatic, 90k miles, all stock. Noticed today pulling empty enclosed car trailer that it seems the tranny is slipping ( I know these are notorious ). Could it also be the throttle position sensor instead? It seemed like with it hardly being under load the tach seemed to be going all over. I did unhook the trailer and took it out tonight and wasn't hardly noticable. Am I crazy thinking/hoping it is just the sensor? Didn't scan it, but dash showing no idiot lights or faults. Tranny flushed/filter change less than 10k ago. Pulled the trailer about 25 miles today, no burning or hot smell.

The sensor will not cause slipping. Sounds like you have internal leakage/slipping. What fluid are you using?

I know it sounds dumb, but I am not completely sure it was slipping, been reading up on it and it may be more of an electrical issue? It just seemed like the was just bouncing around a lot. Local shop flushed and did filter, not sure what they used, but have pulled without issue up til today. The truck does not get driven much. Was not low at all on fluid, and it looked like new. Here is what I am reading on

http://answers.edmunds.com/question-1998...blem-29412.aspx

A friend of mine had a problem with his and it turned out to be the computer. This was after having the trans rebuilt.

could it be front band? what gear you feel it slip?

More than likely the transmission torque converter is going in and out of lock-up. There will be nothing wrong with the trans itself. This issue is from RFI electrical noise interference caused by the alternator being picked up by the TPS circuit going to the PCM. There are several ways to fix this issue. The aftermarket offers a in-line noise suppressor to stop the problem. Me being a cheap a$$, have found another way to remedy ths issue at almost no cost. The first thing you need to do is remove and scrub down your battery cables and post VERY well. This can be half the problem all in itself. After you do this, find the large alternator ground wire goung from the alternator to the passenger side battery box. It will be black w/ an orange tracer. Go into the kitchen and steal a couple of pieces of aluminum foil and wrap this wire several times around from the bottom of the tray to the alternator. This will help shield some of the electrical "noise" from the alternator to the PCM. I have fixed many of them this way without a problem. Give it a shot. You may be surprised.

I agree with 71yella.... been there done that.

My 00 did the same thing, I used the filter. Fixed it instantly.

I think 71yella described it to a tee, I think it is the convertor and not the transmission itself. Won't have time to mess with it for a few days, but will follow his steps and post an update.

Thanks for all the replies, did as mentioned, cleaned all the battery posts, rerouted ground away from alternator and wrapped in foil. Problem solved !!