How to Change a Pinion Seal in a Ford 9-inch Rear End

by Robert Bayly

The 9-inch Ford rear axle is the most popular and most modified axle of all time. You will find 9-inch rear axles in all types of vehicles, even Chevys. The Ford 9-inch rear axle is the strongest rear axle available, deriving its strength from an extra pinion bearing in the axle housing. This keeps the pinion gear on line with the ring gear under high loads imposed by the driveshaft. Changing the pinion seal in the 9-inch rear axle is a fairly involved project, but you should be able to complete it with enough time and the rights tools.

Park the vehicle on level ground. Loosen the lug nuts on the rear wheels. Raise the vehicle with a jack and support it with jack stands. Remove the lug nuts and rear wheels.

Mark the U-joint cap and the pinion yoke with white-out where the cap is seated. Remove the bolts on the U-straps that hold the universal joint onto the pinion yoke. Remove the straps. Remove the universal joint and the driveshaft from the yoke and lower the driveshaft to the ground. Be careful that the caps on the U-joint do not fall off.

Place an inch-pound needle-type torque wrench and socket on the pinion nut. Apply pressure to the torque wrench clockwise and note how many inch-pounds of pressure it takes to move the pinion yoke through a couple of revolutions. Write this value down, as you will need it when you reinstall the nut.

Mark the pinion yoke and the shaft with white-out so you can realign the parts when you put it back together. You will be using a new pinion nut.

Remove the pinion nut (and washer if it has one) by placing a large pipe wrench on the pinion yoke to hold it stationary and using a breaker bar and socket to turn the pinion nut counterclockwise. Note that it will take a lot of force to remove the nut. It is torqued at around 225 ft.-lbs.

Place a drain pan under the rear axle in case any gear oil leaks out when you remove the pinion yoke. Try to pull off the pinion yoke. If you cannot pull it off, use a two-jaw puller to remove it.

Pry out the old pinion seal with a seal removal tool or a small pry bar.

Wipe the area on the axle housing around the pinion seal with a shop rag. Apply a light coat of oil to the inside rubber part of the new gear oil seal. Apply a light coat of gear oil to the outside of the new pinion seal.

Place the new pinion seal against the axle housing and tap it into place using a hammer and seal-installing tool or a large socket that is the same size as the outside diameter of the new seal. Make sure the new seal is completely seated against the axle housing.

Line up the pinion yoke with the painted mark and push on the yoke as far as possible. Install the washer (if it had one) and nut. Tighten the nut with the breaker bar and socket to draw the yoke onto the pinion shaft. After the pinion yoke is fully seated on the shaft, use a torque wrench to tighten the pinion nut to 200 ft.-lbs. while holding the yoke with a pipe wrench.

Switch over to the inch-pound torque wrench and turn the pinion nut. Note the amount of pressure required to turn the nut. At this point the pressure will be less than what you wrote down. Switch back to the torque wrench and increase the torque by 5 ft.-lbs, to 205 ft.-lbs. After obtaining 205 ft.-lbs. of torque, recheck with the inch-pound torque wrench. Keep switching back and forth, increasing the torque by 5 ft.-lbs. until you obtain the same inch-pound force required to originally turn the pinion nut.

Replace the driveshaft and U-joint in the yoke by lining up the marks you painted on the U-joint cap and yoke. Reinstall the u-bolts, washers and nuts. Tighten the nuts.

Raise the vehicle, remove the jack stands and lower the vehicle to the ground.

Items you will need

About the Author

Robert Bayly, based in Apple Valley, California, began writing in 2010, his "how to" articles can be found on eHow. With more than 15 years in the auto industry, Bayly has been an auto and diesel mechanic, service writer and parts manager. He received certificates from Pontiac (parts system), Cat Diesel (engine service), Saab and Fiat (parts- warranty system).

Photo Credits

  • photo_camera Thinkstock/Comstock/Getty Images