Just bought a 1991 Thomas 40 ft pusher with 8.3/643 transmission and drove it 250 miles to get it home. Limited to 68 MPH. is there a work around to get more in the neighborhood of 75 on the flats?
Sounds like gearing then.
Find out what rear end you have and find a carrier with the gear set you want.
Your differential housing will likely have a tag telling you what its got.
Linear Mode
