i have a 74 roadrunner with a 8.25 rear. i bought a nos posi unit for it. i also bought 3.55 gears out of a 96 jeep. the problem is that when i install the carrier in the housing with the ring gear on it the pinion gear will not mesh correctly. am i supposed to use a pinion bearing from a 96 jeep? i have new bearings on the carrier for a 74 roadrunner.