Problem 1. I recently purchased a 1998 Ram 2500 4x4 Cummins. For some reason the transmission started jumping in and out of overdrive or constantly shifting when driving a steady speed of 40 -50 mph on flat ground. Other than that everything shifts smooth. Is there a sensor or something that could cause this?

Problem 2. After the truck is warm, the heat only sometimes blows good hot air. I've changed the thermostat and it's full of antifreeze. Any sugesstions on this problem.

Thanks For your Time,
Chris

 

1. Throttle position sensor.

2. Possible low vacuum. We have to check valves topside. One is for the brake booster, the other is the rest of the truck. I would change both valves, and certainly inspect the rest of the vacuum system. There is a check valve right at the vacuum pump itself, but I doubt that is bad. Not if you are getting intermittent heat. I would guess your blend door actuator is losing vacuum and the air pressure from the fan is enough to push the door over, slightly and let cooler air mix. I am assuming you are running normal engine temp. No chance the thermostat is stuck open? Also I am pretty sure your thermostat mounts sideways. There is a little breather "tit" that has to be at the top or an eternal air pocket can form. Just tossin it out there.


Anyway, those are just my guesses for now.


Good luck with your ride.

 

try changing trans fluid and filter and check all is well in trans and check for loose grounds on frame.mine sometimes gets fussy 40 45 mph seems confused try taking out of od see if that helps

on the heater check heater core id tubing that runs through firewall for pinches or blockages

 

Thanks Demon,

Is the Throttle position sensor easy to access on this truck? Location of check valves?

Thanks,
Chris

 

you gotta a 12v or 24v? either way you don't have a tps. If the trans just started jumping, I would assume that its an electrical problem dealing with the tc lockup.

 

I have a TPS........

 

I just remembered, you probably don't have a vacuum brake booster. Just follow the vacuum line from the pump through it's entire route. The check valve is probably along the firewall somewhere just before it enters into the cab. I don't have a 98 manual to tell you specifics.


The TPS is bolted to the throttle housing. It's the 3 wire device that's bolted to the piece of metal, that the accelerator cable is hooked to. Have someone step on your accelerator, and you will seewhere I mean. The TPS should be held down with 2 smallbolts.

Someonewill chime in with a more detailed explanation, hopefully.


Good luck with your ride.

 

Ooops, forgot that dodge didn't put them on the pedals stupid design. Oh well, you learn something new everyday just to forget it the next

 

Mine is a 24v.

Thanks

 

Cable runs up to the vp44 and under a plastice cover. Never had it off, never looked at it close, but I don't think there is a tps.