I have a 99 dodge 3500 dually 2x4 Trans was serviced about 9 months ago. It has just started this.This happening in the overdrive gears. After 55 mph. It will jump up 200 rpm's then right back down. I gets worst going up hill. I have been told it is the speed sensor in the trans. Do any of you fellows know if this is the problem. It shifts just fine into all the gears. it is an auto trans. The fluid is good and at the correct level
thx

 

It's jumping out of lockup. Any codes?

 

no codes

 

Replace the throttle position sensor.

 

I am thinking it is the torque converter locking in and out

 

Exactly. It's a symptom of a TPS that is having a bad day. (or, series of them.)