Q: How can a pinion shaft oil seal failure be addressed without removing or disassembling the differential on Toyota Land Cruiser?
A: A pinion shaft oil seal failure leads to the leakage of differential gear lubricant past the seal and onto the driveshaft yoke or flange, and the seal can be replaced without removing or disassembling the differential. Begin by raising the vehicle and securely supporting it on jackstands, then drain the differential lubricant and install the drain plug tightly after draining is complete. Disconnect the driveshaft from the pinion shaft yoke and support it out of the way with a piece of wire. Measure the torque required to move the pinion shaft within its backlash using an inch-pound torque wrench, recording this figure for setting the pinion shaft preload during installation. Hold the companion flange stationary with a large screwdriver or prybar, then remove the companion flange nut, marking the relationship of the pinion shaft to the companion flange. Use a two-jaw puller to remove the companion flange from the pinion shaft, and carefully pry the seal out of the differential, possibly using a hammer and punch while avoiding damage to the splines on the pinion shaft. Lubricate the new seal lip with multi-purpose grease or differential lubricant and install it in the differential, using a hammer and a seal driver, large socket, or a short section of pipe of the proper diameter to drive the seal into place. Clean the sealing lip contact surface of the companion flange, apply a thin coat of multi-purpose grease to the seal contact surface and the shaft splines, then slide the companion flange onto the shaft, ensuring the match marks align. Coat the threads of the pinion shaft with multi-purpose grease, install a new nut, and tighten it while holding the flange stationary. Turn the companion flange several times to seat the bearing, then measure the torque required to turn the pinion shaft within its backlash again. The desired preload is the previously recorded torque value plus five inch-pounds; if the preload is less than desired, retighten the nut in small increments until the desired preload is reached, and if the maximum torque on the pinion shaft nut is reached before achieving the desired preload, the bearing spacer must be replaced by a repair shop. After adjusting the preload, connect the driveshaft to the companion flange, fill the differential with the recommended lubricant, lower the vehicle to the ground, and test drive it, checking around the companion flange for any signs of leakage.