So I changed the fluids in the diffs about a year ago...already I have a leak on the rear diff. I used the felpro gasket without any RTV. Both the cover and the axle surface were cleaned and should have been a nice mating surface. I cannot understand why the gasket would fail so soon? I've had other axles where I have not had to use RTV and they have sealed and stayed sealed just fine.

Anyhow, looks like I'll be tackling nasty gear oil shortly in my future (again). So what's best...RTV without a gasket or using both?

 

I've driven mine for ~2000 miles since I did it with just gasket maker (red rtv stuff) without the felpro and it seems to be holding up perfectly fine. My last cherokee lasted like that too. It's probably the only case where I wouldn't recommend a felpro gasket. VCG, pan seal, etc - should all be felpro's, but the rear diffs seem to be just fine with rtv, if not better. It might have something to do with the water that gets onto the top of the diff right where it is on these XJ's - which is why the top few bolts are sometimes rusty/tough to get out. With just the felpro I'm thinking maybe water is getting in there slowly and causing a leak, which wouldnt happen with just RTV. Who knows.

 

I have been changing differential fluid for 15 years using nothing but Fel Pro gaskets on Dana 30/35/60/70 and 8.25 axles and no leaks! I would investigate what may be wrong such as a warped cover before changing the method you use to seal.

 

Hmmm....maybe I didn't torque it to spec. I'll check the cover to see if it is straight or not and let you guys know. Might try the RTV route this go round just to see.

 

It's real easy to distort that thin metal diff cover by over tightening. A gasket with a thin layer of gear oil specific RTV on both sides AND just snug on the bolts has worked for me every time. The cover may need to be straightened.

 

I popped for a lube locker. Less of headache to change the oil, which needs to be done after every water crossing, so why not.

 

IMHO, Lube Locker gaskets are not the best value. Fel Pro gaskets are about $4 at Advance, Auto Zone, etc. If the cover is coming off fairly frequently I have had good luck reusing them.

 

Well looked at the diff again tonight...turns out the felpro is holding fine. It's coming from the front of the rear diff...the pinion seal.

How difficult is this to service? Yes, I can wrench; No I do not have special tools or presses

 

Check to make sure the pinion has no play up down left right. If it does you are looking at doing bearing in the differential. It's important to check because a loose pinion can take out the seal and be an indicator of bigger problems. Also make sure the yoke does not have any grooves that would cause a leak with a new seal. If it does you should replace the yoke. If not and it's only the seal, you can change the seal. Factory procedure calls for measuring the rolling torque of the pinion with the wheels and brake drums removed. Then tightening the pinion but only enough to achieve the same rolling torque. Pinion preload is set by a crush sleeve that will crush if over torqued and mess up the preload. If you mess up, factory procedure is to take the diff apart and use a new crush sleeve. Another way to do it, not factory approved, iis torque the nut to around 160-180 ft lb which should be less than the force to crush the sleeve. If you do this, I would still check the rolling torque to make sure it hasnt changed. You should turn the pinion back and forth as you tighten to make sure the bearungs are seated. Use red lock tite and a new pinion nut.

 

An easy way to cure this is to upgrade the covers to HD Aftermarket ones that have fill and drain plugs on them. I change mine often as I'm off road in wet conditions a lot so drain fluid a lot, its cheap. At least twice a year I pull the covers for a full inspection unless I notice something sooner.


You will find with HD covers they hold a seal better (all I use is RTV) just an idea.


Here is a photo of my D30 cover but have one on the Chy 8.25 also.

 

Thanks md21722, how do you measure rolling torque on the pinion? Not too sure I follow what you are saying there.

 

You need a beam type torque wrench or Torqometer capable of reading INCH POUNDS. The bean type torque wrench. Scale should be between 0-75 or 0-150 in lb. The tool is measuring the force required to the pinion shaft.

 

He's explaining the process of setting up gears. Not something you should have to mess with (hopefully).

 

This is the process used to remove and install a pinion yoke.

 

Well I pulled the yoke out and it does have a groove about halfway down the outer 'race' (for lack of a better word). The nut was not tight either...the correct torque is 150 inch lbs?