[panhead59]

Yeah, you definitely should be getting better than 9 mpg. Time to start checking things out. I agree - start with rearend gear info. If u don't want to r n r cover and change 90 wt. Gear oil ( which i would) just do the tire rotation method. It takes 2 people. Jack it up, mark driveshaft location against rear housing, ( chaulk works good ) . While helper slowly rotates wheel/tire 2 TIMES, count # of driveshaft rotations. It probably will be with a 1/3, 1/2, Etc. Addition to a whole #. Post that # and we can tell u what rear gear u have. Hope i got that right and hope it helps ! Also notice direction of both wheels. If both move in same direction, u have a posi-traction rearend. If one wheel rotates in one direction and the other one goes in the opposite direction, then it's not a posi.