1999 1500 w/318 auto trans @ 116742 miles.

As I travel down the interstate 65-70 mph, the tach bumps as if trans is shifting out of OD. This happens when I deactivate OD (light on), however, the bump in rpm is not as severe. 2 trans shops + the dealership found no codes set under simulation or when driving with the computer monitor hooked up.

I have pulled pop-up campers, bass boats, and cattle trailers and always make sure OD is off.

I will sure appreciate any suggestions.

1999 1500 w/318 auto trans @ 116742 miles.

As I travel down the interstate 65-70 mph, the tach bumps as if trans is shifting out of OD. This happens when I deactivate OD (light on), however, the bump in rpm is not as severe. 2 trans shops + the dealership found no codes set under simulation or when driving with the computer monitor hooked up.

I have pulled pop-up campers, bass boats, and cattle trailers and always make sure OD is off.

I will sure appreciate any suggestions.
My 1998 had a similar problem. With cruise control on the rpm jumped intermittently about 150 rpms.I replaced the Throttle Position Sensor, about $35 at NAPPA. this seems to have fixed the problem.

That is the best place to start often tps{throttle position sensor} when faulty voltage will change {when holding accelorator steady} too fastfor scan tool to display voltage change so it is very difficult to verify faulty sensor. Now you canhave it checked with a lab scope or perform co-pilot tests at much more cost or take a chance and purchase a new tps they are not too costly and very good chance this is your problem.