I'd agree that your problem is far more likely to be your rear u-joint than the pinion bearing. Disconnect the driveshaft and feel for any roughness or resistance when moving the u-joints through their range of motion. Any slop or anything other than nice smooth movement means it's time for new u-joints.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes