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Toyota Pinion Seal Replacement

A gear oil leak around the base of the pinion flange on the front or rear differential (or even the transfer case) is a sign of a leaking seal. You should first check the the axle breather tube is free and clear, if not it can allow pressure to build up inside the axle and force oil out past the seal.

First step in removal is to loosen the four "companion flange" bolts that hold the driveshaft to the pinion flange. Use a pair of long handled 14mm wrenches to break the nuts free and remove the 4 bolts. Set the end of the driveshaft to the side, being careful not to let it separate at the slip yoke.

Check that the pinion flange nut is tight, if not, it can cause the pinion flange to move around under load and cause the seal to leak. If it is loose, tighten to ~90 ft.lbs. torque with a 30mm socket and torque wrench. This is easiest to do with the 3rd member still installed in the axle housing. Then you can use the e-brake and vehicle weight on the tires to resist the loosening torque on the pinion flange nut.

If the above checks are fine, then proceed to replace the pinon seal, see below for the replacement steps:

 
  If you have a relatively low pinion angle (i.e. the pinion flange is below the level or the gear oil fill hole in the axle, you might want to drain some gear oil or be prepared to catch whatever comes out of the pinion shaft hole. Elevating the opposite end of the truck may help contain the oil. Then, un-stake the pinion flange nut. Use a 30mm socket to remove the pinion nut, count the number of turns needed to remove it and reinstall with the same number to retain the pinion bearing pre-load. With the pinion nut, washer and flange removed, the pinion seal is revealed. You may be able to remove the seal with a flat-bladed screwdriver, but be very careful not to damage the pinion shaft in doing so. I chose to use a seal puller like this to remove mine. I picked it up for about $7 from Harbor Freight. You slip the end of the puller along the pinion shaft, catching the lip of the seal, then use a hammer to tap on the T and pull the seal out.  
 

 
  I used a new seal from Toyota, p/n 90311-38047. Be sure to apply some grease along the inside of the seal lip and make sure the pinion flange sealing surface is not grooved. If it is the new seal may leak, a new flange is available from the dealer. I found a 50mm socket that worked well to push the new seal into place. A rubber mallet may work as well, tapping gently around the periphery of the seal to seat it evenly. To help prevent leaks, you can apply some RTV silicone sealant to the splines of the pinion shaft prior to sliding the pinion flange on. Reinstall the flange, washer and nut. If the old nut is in decent shape, it can probably be reused, if not a new nut is available from the dealer. Tighten the nut the same number of turns as it took to remove it and tighten no more than about 90 ft.lbs. or until the stake mark aligns with the groove in the pinion shaft. Check the flange for play and for being overly tight. If it feels OK, re-stake the lip of the nut with a punch and hammer to keep it from loosening up, then re-install the driveshaft bolts, tighen to factory spec. (~54 ft.lb.) and you are done. If you drained the gear oil, be sure to replace it before driving, approx. 2.5 qts. of GL-5 should do it.  
 

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