My rear diff housing is leaking quite badly. is it possible the pinion seal is the problem

loosen rear wheels, jack up rear so wheels are free, fit safety stands , drain oil, remove wheels, remove 4 bolts holding axle bearings. remove both axles, remove bolts from tail shaft at diff pinion flange , leave tail shaft in transmission housing or oil will leak out, remove bolts from diff housing, the diff center can now be removed.

Ok...a leak in the front diff seal could not have been caused by an axle bearing/seal replacement. However, as I stated, the fluid level should have been checked after the job was completed. Further, front (called a pinion seal) leaks do not happen all of a sudden, rather they seep fluid for quite some time before failing. (unless the outer or inner pinion bearing has failed) THAT should have been easily noticed by the tech while he was working on it.
If the differential is noisy, I would not bother having the seal replaced as noise (usually howling or grinding) indicates a gear or internal bearing problem that is very expensive to repair. If you are at that point, best to obtain a used unit, end to end, (of the proper ratio) and replace it with that.
Depending upon what kind of flange or yoke you have on the diff, the seal is replaceable and inexpensive (less than $20). but you need some mechanical ability and proper instructions to do it.If done improperly, you will destroy the gears.

this is very hard if you do not know what you are doing. Ill try to step you through this

• pull wheels
• drain pun-kin case
• pull rear cover
• in between the spider and axle sets pull C ring with needle nose pliers
• pull hub and axle out CAREFULLY as there are roller bearings on the end of the axle housing
• pull seal out at the end of axle housing
• tap in new seal CAREFULLY and straight DO NOT BEND IT or it will be junk
• replace axle carefully as the roller bearings are still there
• replace C clip to original position
• replace axle diff cover and replace the gasket with a new one
• refill diff case
  
• install tire
• your good to go
  

leaking where? axle shafts? pinion seal? diff cover?
should inspect diff internals and bearings-may require overhaul not just
seal replacment. also check vent tube-if plugged will cause all seals to leak.

That would depend on where on the diff. the leak is coming from. If its leaking where the driveshaft connects to it, then it's a pinion seal. If it's leaking near the wheels, it's an axle seal, and if it's leaking where the cover is, it's a bad cover gasket. If it's the cover, you can reseal it with RTV gasket maker.

The only place you did not mention is the pinion seal (at the yoke where the driveshaft connects) Any leak from a differential should be fairly obvious...clean everything off well and drive it, You should see seepage somewhere. Any grease on the wheels or new fluid where you cleaned will tell you where to look. If it is at the pinion seal, If you haven't done this before, don't...you can disturb the adjustment inside the gear case and damage the gears.

the part is called the pinion flange seal, pull the drive shaft, remove the large nut on the flange the drive shaft connects to and remove the flange, then pry out the old seal and lube the lip of the new seal with motor oil and press it into the opening. The 7.5 hour estimate is way wrong, about 1.5 hours labor and $4 for the part.

To replace the seal you must pull out the carrier assembly and the pinion gear and install a new crush sleeve if you do it by the book, I have found that if the yoke is removed a new seal installed and the yoke tightened to about 50 foot lbs of torque it is ok, as far as the lube goes there is a plug on the cast case of the diff, it will either be a square drive plug or a large allen plug, fill the diff so you can just touch the fluid with your little finger, don't overfill or the axle seals will start leaking.

check your rear diff vent if pluged clean it out and clean up the pinion seal.sometimes if the leak is caused by pluged vent and has not been leaking long once vent is clean sometimes the leak will stop.there is not a specific torque amount because it is rotational torque(how hard to turn pinion).there is a crush sleve on the pinion and if torqued too tight or too loose brg preload will be wrong and brg damage could result.mark and remove drive shaft.remove rear wheels,brakes,axles.so when turning pinion you dont have any drag from brakes or axles.mark the position of the yoke on the pinion.remove yoke,replace seal,reinstall yoke be sure to replace pinion nut.tighten nut until it takes the exact same amount of force to turn pinion as before taking original pinion nut off.hope this helps.

You don't have to remove the whole diff to change the seals, but you will have to seperate it where the shaft meets the carrier housing. There is a clip holding the passenger axle shaft in place that you have to remove to change the seal. The drivers side axle stub can be removed with a little force as there is a spring clip holding that side in.