I have a 1997 3500 4x2 cab/chassis that I use to haul expedited freight. I currently have 512,000 miles on it. I replaced the automatic transmission last year in Marshall, TX (I am from Indiana.......long expensive story). It is a factory rebuilt unit (longer warranty and cheaper than a brand new one). I have put approx 60,000 miles on the new tranny. I am now having problems with it surging and hunting for gears. It occurs at speeds between approx 45 and 53 MPH. It only does it if I am trying to drive at those speeds. If I am accelerating hard to get to highway speed it never gives one hint of a problem. Nor is there any problem at lower speeds. Tranny fluid level is fine and looks good. Does this sound like a TPS or tranny problem?
Thanks for the help.

 

If you want your tranny to last push the OD off button until you exceed 55 mph.
It won't hunt then and is easier on the torque converter.

 

Sounds like a TPS issue to me. Mine did almost the exact same thing a while back. It would hunt for gears at near-freeway speeds, but if you floored it, no problems.
Local shop that I have trusted for years told me it was the tranny. This was when I first bought the truck and was really clueless, before I even found this site. So I believed them and replaced the tranny. Still identical problem!
They took it back and checked it over a few times, then I found this site and someone mentioned the TPS. I went to Dodge, bought a new TPS and never had any more problems.
I believe there is a test you can do on the TPS with a voltmeter to check it. I think you can find it on www.dodgeram.org

 

Thanks squirlchasr. Do you recall how much the TPS was and was it fairly easy to replace?

 

I wanna say the TPS was around $200 from Dodge, much more than a gasser would be. Also a fairly expensive proposition in case it's not what's wrong.
Here is the link to checking the TPS:
http://www.dodgeram.org/tech/transmi...TPS_adjust.htm

It is fairly eas to replace, it only took me a few minutes.

 

Several things come to mind for your symptoms, I will Assume this problem just started recently. Driving habits, turning off OD below 55 will extend the life of the trans greatly. second, the tps could have a flat spot at that particular position. Do a test from idle to wot position to check for opens or flat spots. Third, how long has it been since you serviced the trans? Do a complete flush and filter change. The type of driving you do, you should flush the trans every 15,000 to 20,000 miles, REGARDLESS of how clean the oil looks. If the filter is doing its job and catching all the wear materials, it will cause the trans pump pressures to run a little low, causing the trans shift to change, reduce the pressure on the clutch packs causing slippage, causing the fluid to burn causing the filter to really plug, dropping the pressures even lower ...... til the trans totally fails ,,,again. Do some price comparisons. The cost of a flush and filter, $120-150 per 15,000 miles or $3500 per 100,000 miles for a transmission. Good maintenance is key to longevity. Good luck

 

Between the two of my 1st gen's, I have replaced the TPS six times. I took the '93 to the shop because I had similar experiences with surging like you are. They told me I needed a new tranny. So, new tranny, same problem. Changed the TPS, good as new. Their expensive and don't last long. My father has tried tapping them with a ballpean hammer and drilling a hole in the casing for a WD-40 nozzle. Don't work.

 

Thanks for all the advice. My initial failure was due to a couple of the transmission cooler lines touching each other which eventually lead to a whole in one or both causing my transmission fluid to be pumped out somewhere between Indianapolis and Houston. The transmission temperature light never came on but works everytime I turn the truck on. The fine folks at Patterson Dodge in Marshall, TX set me up with a factory reman tranny and new coolant lines for about $4100. I don't know how bad I got took but I was 800 miles from home and everyone was super nice.

 

It sounds like the TPS. As far as prices go check out www.rockauto.com I paid $155 a couple weeks ago.

 

I had the same problem, transmission lines rubbed into. Replaced some lines and the temperature sensor. Trans started surging and no overtemp light. Since my transmission was not doing it all the time, I tried lots of different things to defer the trans overhaul cost.

The only thing the Throttle Position Sensor (TPS) is used for in the Diesel truck is for shifting (up & down) the transmission. Replaced mine - no help. The trans overtemp light eventuallly came on and I put a wire down the dipstick connected to Fluke 52 Thermometer to monior the temp. Never got above 180 deg F.

Found out that the transmission was sending a false overtemp signal to the computer, causing the transmissing to downshift to cool off the trans (surgging). The connector at the trans temp sensor was not making good contact causing the problem.

 

Thanks Rick
I still haven't had a chance to run the test on the TPS yet so I will check out the temp sensor connector if TPS checks ok before buying another TPS. That could save me some $$$$$.