as i'm driving at 60+mph, it seems like the tranny down shifts and the tach revs up to about 3000rpm, then goes back down, then back up and so on. What could be causing this? Tranny was recently rebuilt
tach surges at 60+mph on 1990 Dodge Dakota
Sounds like a possible issue with the torque converter or torque converter clutch. I would advise you to return to the place where the transmission was rebuilt and have them recheck their work.