Dmouse1

The front differential seals leaks and I need to know how to replace that seal without going to the dealers shop...

jaggerwild

Hey Dmouse1,
Its pretty cut and dry, remove the bolts drain the old fluid. Go to your local parts guy first pick up a new gasket for it, also get several bottles of heavy gear oil aswell.(He can tell you what weight you need for your truck).
Thats about it....
Let us know if we have helped you.

Dmouse1

I mistakenly led you to believe it was the differential that was leaking, sorry for that, it is the pinion seal that is leaking...

qldit

Good Morning Dmouse1, generally the pinion seal can be replaced without much difficulty by rmoving the drive shaft, undoing and removing the drive shaft flange from the diff and levering the seal out.

Carefully inspect the drive flange seal wiping area for wear and any grooving and repair as neccessary, usually carefully rotating the wiping area and flange in a piece of handheld fine wet and dry abrasive paper removes any ridging in wear areas, clean the seal seating area in the diff and fit a new seal and reassemble.

When diff seal leakage is excesive it can be caused by pinion bearings looseness, but replacing that seal does allow temporary problem fix even if this were the case.

Seal leakage can be amplified if universal joints are eccentric or worn and out of balance or the propellor shaft is not runing true.

This kind of job is not usually all that difficult, you may need to have the wheels on the ground to undo the drive flange nut on the pinion shaft, it should be pretty tight.
The flanged section normally is on the splined pinion shaft and should come off without problem once the nut is undone. Check the torque tension figure before reinstallation and ensure that nut is tightened appropriately.

Check diff oil level afterwards and you may need to top it up.
Make sure you use appropriate oil if this is required.

Cheers, qldit.

Dmouse1

Thank you qldt that helps tremendously and it sounds like something I can handle myself, I will retain these instruction to refer to...

qldit

Good Afternoon Dmouse1, that is a general description of the process, I am not familiar with that particular vehicle but expect it would be a similar arrangement.
You will know once you start the job, it is generally not all that difficult if it follows that normal pattern.
You may need a puller to get the flange off the diff pinion shaft, sometimes they get a bit of rust in them and may be a little bit tight.
With the right tools it is probably a couple of hours work in the backyard.

When you loosen the drive flange you can raise the front of the vehicle for a bit more room if needed and may get a bit of diff oil run out, do use jackstands or extra supports to safety the work area. Those machines can be pretty heavy.
You will need to have the wheels back on the ground to retighten that pinion shaft nut and the hubs locked.

Inspect the universal joints when you do this work and if there is any suspect, replace them.

Hopefully you will have a smoothe job with no hic-cups!

Cheers, qldit.

Midnight Tech

Make sure you pick up a new crush sleeve for the pinion...those can't be reused.

Dmouse1

will do MT

DaChew

This is an old thread. I came across it via google and I thought I would clarify and amplify some of the information to make it a little more complete.

First off, contrary to the above, you do not need a crush sleeve - You will not be removing the pinion. Nor will you be opening the differential.

To change the front differential pinion seal on the 99 Silverado you would do the following:

Remove the negative lead off of the battery. The truck will be in neutral most of the time and that means the key will have to be in the on position and that means that many of the electrical systems will be active and that will drain your battery. Jack the vehicle up at all four corners. This will make it easy to spin the driveshaft while you're under there. If your truck is a Z-71, remove the skid pad beneath the front axle. Drain the differential by removing the drain plug. If you don't, the oil will drain on you when you remove the diff seal. Get a white or silver paint marker and mark the position of the driveshaft as it connects to the flange. You want to put everything back exactly the way it was when you reassemble - even the U-Joint cap straps. Remove the four U-Joint strap bolts - this is where being able to spin the driveshaft by hand comes in handy. You can spray penetrating oil on the caps if they're rusted to the flange to help get them loose. You don't have to remove the shaft at the transfer case, simply wire it up out of the way of the diff flange. Now mark the position of the flange nut, count the threads showing and check the resistance of the flange turning with a beam torque wrench - you can also use a click torque wrench by setting it so it clicks just as the flange begins to turn. Now you have to decide how you're going to hold the flange while you loosen the flange nut. There are tools at the local auto parts store to do this, you can use a strap wrench, a large pipe wrench will work, you can take one of the U-Joint straps and use it as a template to drill a couple of holes in a length of steel and bolt it to the flange - up to you. You are going to need a breaker bar to get that nut loose though. Remove the nut. Use a two jaw gear puller, 3" or 4" inch will work, to pull the flange from the pinion. I have a rigid paint scraper that does a dandy job of working itself under the lip of the seal and levering it out. I can even use it to pull a seal without damaging it by working slowly. You can also certainly use a screwdriver or small chisel and remove it by prying it out it if you like. Just be careful of what you are jamming in there, there are bearings right on the other side of the seal. Once you have the seal out, be prepared for gear oil to drip out - it will, even though you've drained the diff.. Clean the area with some paper towel. Grease the back side of the new seal lips, smear some gear oil around the seal where it contacts the flange. There will be old RTV sealant on the pinion splines and inside the flange, clean that up. Inspect the area where the flange contacts the seal and clean it lightly with some sandpaper if there's a ridge. Apply some new RTV, just a small bead to seal the splines, on the inside of the flange. You should be able to press the new seal mostly into place with just your hand. Then you can use a really big socket or seal driver to press it the rest of the way in - I prefer a 1" wooden dowl and light taps with a rubber mallet to seat the seal. Line up the flange on the pinion splines according to your marks and press it on until you can get the washer and nut on. Hold the flange from turning and tighten the nut to draw the flange onto the shaft. Tighten the nut until it seats. Check the number of threads showing, use your torque wrench to get it back to the same resistance when turning (The new seal will add a small amount of resistance so, keep that in mind). When it feels right, your set, reconnect the driveshaft according to your marks, refill the differential, put the skid plate back on.