I have a 98 Dodge Ram 2500 2WD with 5.9 gas engine. Originally I had the ABS and Brake lightstay on. Also the speedometer didn't work until the speed reached about 35. I took it to a mechanic that told me the ABS computer was bad. Searching for another answer I found this forum with suggestions about the speed sensor on the rear differential and the output speed sensor on the transaxial. I changed both and the ABS and brake light are now out, however the speedometer is acting very strange. When I accelerate the speedometer stays about 5 mph. If I let off the gas the speed goes up to about 35 or 40 but goes back down when I press the gas. It also has the typical shift problem going from 1st to 2nd it will shift about 2500 rpm or higher if I trying to accelerate quickly. Any ideas? Thanks

 

did you reset the pcm after changing those sensors. if not, i'd try that first. disconnect neg battery cable and turn and hold key to start for 30 seconds. that might help, might not.

have you got the digital odometer ? i can't remember the year it started if so, do the gauge test. hold trip meter button in while turning key to on. continue to hold trip meter in until it says 'chek', then let go. cluster will self test, turn all lights on, and finally and most important, it will sweep the gauges in 3 steps to about 1/4, about 1/2, and then full. if your speedometer fails this test, then the problem is all inside the cluster. if it passes this test, cluster is ok.

mine would sometimes work/sometimes not (typically when sitting in HOT summer sun). when speedo would not work, it would also fail the cluster test above. based on that failure, i replaced the cluster with one from junk yard for $25.

 

Thanks for the reply.

I do have the digital odometer and checked the cluster. Everything worked as it should so I think that is fine.

I reset the pcm and still have the same problem. I also installed an ABS computer I got from a junk yard but still have the same problem.

To summarize the problem: speedometer registers about 5mph when driving. When I coast the speedometer goes to about 35 - 45. When I press the gas it goes back down to 5. There are no warning lights on. The transmission also doesn't shift right going from 1st to 2nd. The RPMs reach between 2500 and 3000 before it shifts. Not sure if that is related but it started happening about the same time. Any other suggestions?

 

I know you mabye don't want to do this again. But I am willing to bet that it is your speed sensor on the transmission. While the ABS sensor in the rear axle can cause the same effects, your ABS and Brake light are not on. Its a small possibility that it could be the ABS sensor is bad. Its probably the speed sensor due to your problems. The high rpm shifting and speedometer trouble. Try changing it and post the results. I could be wrong on this, but it is the most logical right now.

 

Sorry for the slow reply but thanks for your suggestion. I haven't done that yet since on the way home Friday the brake and ABS lights came on again. Now they seem to be off when I start the engine but come on after about 10 min. I'm planning to take it somewhere to have the codes read and then post the result.