Pinion Seal Replacement

Pinion seal replacement is something that you probably haven’t done before.  Seals in your differentials or axles don’t often leak, but when they do the best way to stop the leak is to replace the seal.  Seals often leak due to wear but they can also leak from a lack of use as is the case in the Nissan Armada in this video.  The pinion seal we replaced was in the front differential which only engages when you put the truck in 4 wheel drive.

A pinion seal replacement is different from an axle seal replacement because removing the pinion flange has the potential to change some of the geometry in your differential.  On any differential, the orientation of the pinion gear to the ring gear is critical.  If the pinion gear is set too deep or too shallow the gear mesh pattern will be off will cause noise and poor gear wear.

Besides affecting the wear pattern, the pinion bearing preload is also affected by how the pinion flange is installed.  If the pinion flange nut is too tight there will be too much or too little preload on the bearings causing noise and accelerated wear.

Before we talk about installing pinion flange, it’s important to mention some tricks for removing the pinion flange:

Pinion Flange Removal

1. Mark the driveshaft before removing it so you can install it in the same orientation
2. Measure the distance from the end of the shaft to the surface of the nut as a way to make sure the pinion flange is reinstalled to the same depth
3. Try using an impact wrench to remove the pinion flange nut
4. If you have to use a breaker bar try using a fan clutch holding tool or pipe wrench to hold the pinion flange
5. Once the nut is removed you may still need a puller to remove the flange from the differential.

Once the new seal is installed, it’s time to reinstall the pinion flange.  The best way to make sure the pinion flange is reinstalled correctly is to check your vehicle’s repair manual as different manufacturers have different methods of determining bearing preload.  Some differentials use pinion flange depth while others may use turning resistance.

Once you’ve got the pinion flange installed correctly it’s as easy as reinstalling the driveshaft in the correct orientation and refilling your differential if any fluid leaked out during the seal replacement!

If all this has got you scared, you might consider using BlueDevil Oil Stop Leak to seal your oil leak instead!