i have a 98 dodge ccummins 24v 3/4 ton 4x4 and when driveing warm and empty at about 40-45 miles per hour the trans stutters pushing then lowering the rpms and when i have any trailer or weight on it does the same thing at 35 to i replaced the valve body and checked the tps sensor after the valve body it helped a little then went right back what do i check

 

It sounds like the torque converter is locking/unlocking on you. Does the tach jump around about 200-300 rpm?