What's involved in changing rearend pinion seal?
 

I posted this in the "Other Drivetrain" forums but I don't think that forum is visited as frequently as this one. So I figured I'd try here. I found out today by a mechanic that I have a leaking rear-end pinion seal on my 3.55 non-LS open diff. I am going to buy the diff fluid and seal. I already bought a pinion seal at Advance Auto today for about five bucks. And the mechanic says he'll replace the seal for $35. What I need to know is how many quarts of differential fluid (rear-end oil) do I need to buy? And where can I find the 75W-140 synthetic diff fluid that I need? I went to a Napa Auto parts place today and all they had was 85W-90 regular diff fluid. I just basically want to know what all I need to buy to have this repair done. Thanks. Any help is appreciated! :(

First of all you dont need to replace the differential oil unless you choose to.Wal-Mart sells 75W140 synthetic oil for about $9.00 a quart,and is some very good oil.You might want to get one quart to top off the differential.
To replace the seal,first,raise the rear axle,remove the tires,and support the axle on jack stands.Mark the orientation of the driveshaft with the pinion flange.Remove the driveshaft.Take a torque wrench and check how much torque in inch pounds it takes to rotate the pinion shaft.Record this for later use.Count the threads exposed past the pinion nut and record for later use.Put alignment marks on the pinion shaft,nut,and flange.Use a screwdriver thru one of the pinion holes to hold it as you remove the pinion nut.If the pinion flange wont slide out you will need a puller to remove it.DO NOT HAMMER OR PRY ON THE FLANGE! Pry out the old seal.Lube the outer edge of the new seal with grease and use a large socket or seal install tool and tap it in squarely until it seats properly.Re-install the flange,marks lined up from earlier.Use the nut and washer to pull the flange in,if needed.Apply some non-hardening sealant to the pinion splines in the center of the flange so the oil will be sealed in.Install the washer and nut and tighten until the exposed threads are what you recorded earlier.Measure the torque required to rotate the pinion until it matches what you recorded earlier.Then,tighten the nut just a bit more,not to exceed 5 inch pounds.Re-install the driveshaft.Top off any lost fluid.Put the tires back on,lower it and test drive. :santa:

Thanks for the step-by-step procedure BlueOvalFitter. But I won't be doing it, my mechanic will. But I found out what I needed to know. Thanks for the help!

I checked the rear-end gear oil today and it used about 1/3 of a quart. I bought some 75W-140 synthetic gear-oil at Wal-Mart ($9.35 per quart) yesterday and topped it off until I get it to my mechanic. It's not leaking very fast anyway. I'll just keep an eye on the oil level until I can take it to be fixed hopefully sometime after New Years. ;)