On the highway my rpms will jump up and down, and sometimes the tranny leaves itself in to high of a gear, like in parking lots. My truck is a 1995 with 95000 miles, automatic tranny, and 4x4, if that would help figure out the problem. I have read that it might be something to do with the throttle position sensor but where I read that they were trying to sell me something so I dont know if I should believe that. I would like to know if this is something serious or should I just ignore it.

Thanks

 

It would be best to repair the surging problem. If the trans is shifting, causing the surge, the most common cause is the TPS. If the eng surges in one gear without shifting, or when reving in neutral, it would be most likely fuel supply problems. ie fuel filter, fuel pump, overflow valve. If your trans oil is dark or burnt, change the oil and filter. Good luck

 

It sounds like a TPS problem. There's a procedure to check it outlined in the Tech Facts under the 12 Valve Drivetrain section. Some guys have had luck cleaning the TPS with some electrical cleaner. They're pricy little devils. They are a Cummins part so they might be cheaper there than at Dodge.
A couple other things to check for are a bad brake switch and your Vehicle Speed Sensor connection (3 wire plug on the driver's side rear of your tranny).

 

tps..its a common thing

 

The tps may fix his shifting problem on the highway , but it's not going to help him with it gettin stuck in a high gear in a parking lot , that is a VB problem , and we all know how to fix that...

mchydro, next time it starts upshifting/downshifting on the highway , press the o/d off button, you can also test the tps , as outlined in the tech facts , your looking for .7-.8 ( i just replaced my tps , it was giving me .15v at idle, and a maximum voltage of 1.5 at full throttle) and the voltage should smoothly increase to 3 or 3.5 volts at full throttle.

 

Thanks for the help! How would I fix the valve body problem?

 

Its really not a "problem" as much as a characteristic. My truck kinda likes to shift to quick too sometimes. Just pull the shifter manually down into 1st. As for your "surging" it is your torque converter unlocking/locking. Changing my tranny filter/fluid fixed that problem on mine, so you might try that first on yours, and then go to the TPS, since changing the fluid is a good thing to do anyway. You can clean the TPS and sometimes fix it like that instead of buying a new one. Just do a search on it. Good luck!

Eric

 

Afaik, about the only fix for a vb , is to replace it , either with a stock one (add a shift kit to it , you will be very impressed) or go with an aftermarket VB , they are actually not that expensive considering what you get.

 

I forgot to mention to check your Throttle Valve cable for proper adjustment. Might be why it's staying in too high of a gear at low speeds. Directions are here TV Cable