domgbrl

It is a auto truck. I scanned it with a OTC Encore scan tool. It happens most at a small part throttle condition, i can barely feel it driving on the highway, but when i tow my trailor it becomes more noticable. If i give a little more throttle it goes away

I scanned it, no codes yet

99 2wd 3500, auto. Pretty much stock with exu and a air filter.

Crusing at 1800 rpm, the tach needle is bouncing/ jumping up to 2000 rpm. And when this happens the truck seems to be bucking and jerking slightly. Any ideas??