I recently purchased a 1996 Ram 3500 diesel 4x4 clubcab with auto. The transmission shifts great 1 to 2 and 2 to 3, however it only shifts to 4 if you keep on the throttle, and downshifts to 3 if you let up on the throttle. It will not kick down for passing gear as it is in third, but will down shift to 2 when speed is about 35 mph or so. It runs great in third but guzzles diesel like crazy. Does any one have any suggestions as to the problem. I have built a number of 727 transmissions and this one looks to be like the 727 except for the overdrive, which adds a whole new area.


The electrical problem I think is a bad connection somewhere. The airbag light will come on at odd times and the heater blower will shut down when it does, after the heater blower shuts down the ABS light comes on. After a short period, about 15 to 30 seconds or so, the airbag light goes off and the heater blower comes back on and shortly after that the ABS light goes off. I can drive the truck over a hundred miles with no problem and then while it is setting still this all happens, or it will happen while moving and may repeat several times in a short time frame. As you can see it is very random which suggests a wiring or connector problem. I checked my shop manual and none of these use the same ground point, they use G101, G107 and G202 and different circuits as near as I can see so far. Does anyone have any ideas?
Thanks for any help on these .

 

Shifting problem is just strange. Have you tested the throttle position sensor?

Check the connectors at the PCM for your other odd problem.

 

If there is an issue with your speed sensor it can cause od problems. Od should engage approximately at 45 mph with low-moderate throttle. Did you check all the fuses/connections in the fuse box next to the engine compartment?

 

I checked all of the fuses and they are all good. The speedometer works ok and is accurate. When I use cruise it hunts back and forth between 3rd and 4th. I have not tested the throttle position sensor, I will do that tomorrow, I will also see if I can locate the test procedure for the speed sensor in my manual. Thank you both for your suggestions, I will update with what I find.

 

Sorry this took so long, lots of snow to plow plus not fun to work on truck outside when it is snowing and the wind is blowing.
I checked the grounds and cleaned them all under the dash and in the engine compartment, no more problems with the heater blower and ABS light.
I checked the TPs as outlined in the factory service manual, had readings all over the place with nothing consistent. I pulled the TPS and retested for voltage change as is indicated in the manual, it worked from 0 volts to 5.0 volts, no problem with the sensor.
I pulled the throttle bracket off the engine, the shaft bushings were very loose, the end of the shaft that turns the dogs in the sensor was worn down where it would slip by the sensor dogs, and there were no throttle return springs.
I was able to get the bushings and the springs from CARQUEST and I used my mig to weld up the shaft and filed it to shape. Now the voltage runs from 1.06 at idle to 3.75v at WOT, it shifts to 2nd at 15 to 20 mph and to 3rd at 25 to 35 mph and into od at 45 to 55mph depending on throttle pressure, cruise works great and it seem to run out good. The throttle returns to idle at 650 rpm now instead of changing every time you were at idle.


Thanks for your help and suggestions on this, I would never have thought to check on the TPS for this problem.