How to Fix a Leaky Pinion Gear

The pinion gear on a rear-wheel drive vehicle is driven by the driveshaft. It is part of the rear-axle assembly and drives the ring gear which in turn drives the axles. The pinion gear has an oil seal that fits into the rear-axle housing. A bad seal will allow gear oil to leak out of the axle housing which can lead to failure of the pinion bearing and entire axle assembly. The pinion gear seal can be replaced without taking the axle assembly apart.

Instructions

1

Park the vehicle on a level paved surface. Loosen the lug nuts on the rear wheels. Block the front wheels with wheel chocks. Raise the rear of the vehicle and support with jack stands. Remove the lug nuts and rear wheels.

2

Use a wrench to remove the nuts from the U-bolts where the rear of the driveshaft attaches to the pinion gear yoke. Remove the nuts and washers. Remove the U-bolts. Slide the drive shaft forward and out of the pinion yoke. Move the drive shaft off to the side and let it rest on the ground. Be careful that the bearing caps on the U-joint do not come off.

3

Use white out to paint a line across the edge of the pinion gear to the yoke. You will match up the lines upon reassembly.

4

Place a socket on a beam-type inch-pound torque wrench and mount it on the pinion nut. Measure how many inch-pounds of torque it takes to turn the pinion gear. Write it down on a piece of paper. You will need to refer to it later.

5

Use a large pair of channel-lock pliers to hold the yoke while using a ratchet and socket to remove the pinion nut and washer from the pinion gear, in the center of the yoke. Attach a two-jaw puller to the yoke and pull the yoke from the pinion gear.

6

Look at the pinion seal so you know which side will be facing out when you put in the new seal. Stick a flat screwdriver through the rubber part of the seal and pry it out of the axle housing.

7

Clean the axle housing and pinion yoke with a shop rag.

8

Place a light coat of wheel bearing grease on the outside rim and inside lip of the new oil seal. Use an oil seal installer -- rented from a parts store -- to drive the seal into the axle housing by tapping the end of the installer with a hammer.

9

Place a light coat of grease on the splines of the pinion gear and the outer surface of the yoke, where it will be sliding into the oil seal. Line up the marks on the pinion gear and yoke and tap the yoke onto the pinion gear far enough so that you can install the washer and a new pinion nut by hand.

10

Hold the yoke with the channel-lock pliers and tighten the pinion nut just enough with the ratchet and socket so that there is no end play -- in and out movement -- of the yoke and pinion gear. You will have to tighten a little bit at a time and stop to check. When all play is removed, turn the yoke a few times by hand.

11

Use the inch-pound torque wrench to see how much force is needed to turn the yoke. Your desired reading is your original measurement plus five inch-pounds. For instance, your original measurement was 20 inch-pounds. You now want a measurement of 25 inch-pounds. If the measurement is not high enough, tighten the nut in very small increments. Very small means about 15 degrees of rotation, or the distance on a clock face from 1 to 2 o'clock.

12

Mount the drives shaft and U-joint in the yoke, install the U-bolts, washers and nuts. Tighten the nuts. Raise the vehicle, remove the jack stands and lower it to the ground.