I have a 2002 Dodge cummins one ton with a automatic transmission in it. When I bought this truck 2 years ago the man said he had the transmission just rebuilt. I do not use the truck much and have only put about 3000 miles on it in the last 2 years. After letting it sit for about a month after getting the truck it would not move into gear and I tried to contact the guy I bought it from to see who rebuilt the transmission but he had moved and no longer had the same cell phone. I was told to crank it up in N it would then go into gear without any problem which worked. Now the other day I was hauling some soybean seed and when it got to 45 MPH it shifted and being in a 45MPH speed zone I was doing 47MPH. It looks like the transmission could not figure out what gear to stay in. It would shift up then down then up then down and when I got to 52MPH it stayed in one gear. When shifting up and down the speed would stay the same but the RPM of the engine would go up and down about 200RPMs. On the way home I got in several 45MPH speed zones and at 42MPH it stayed in one gear but if I went above 45MPH it would shift up and down every 3 seconds until I got over 52 MPH. This is with O/D on or off it does the same. Has anyone had this problem and could point me in a direction of where to start looking for the problem. I just change out the power steering pump about 100 miles ago. I never saw any paperwork showing the transmission had been rebuilt but when I looked under the truck, the transmission was clean top to bottom. Have not used the truck to tow anything heavy. Thanks

 

Your torque converter is locking and unlocking. First, clean ALL your grounds. The engine, batteries, frame, ect. There are a few other things you can do, but start with cleaning your grounds, it doesn't cost anything to do that yourself and it should be done anyway.

 

OK Brain thanks for the direction to start looking for the problem. When I got the truck the battieres would go dead after sitting 2 weeks and I could never find what was draining them. so I put two battier disconect switches on the ground side of the two battieres to solve the problem. Since I use the truck very little it solved the problem of the battier drain. When i need the truck I just open the hood and tighten the disconect to complete the circuit. Looks like the black and yellow ground wire for the transmission connects to the battiers ground on the passenger side battier. I went out to the truck this morning and tighten the disconects and made sure the one on the passenger side was tight. Took the truck down the road and back and the transmission shifted like it shoule. Thanks for the info. Looking at you tube I saw where a guy had the same problem back a while ago and spent $2400+ on transmission rebuild trying to fix it with no luck.