Jeep Cherokee XJ - Dana 30 and Chrysler 8.25 Differential Fluid Change

When I purchased my Jeep, I didn't know the last time the owner changed the differential fluid. According to the Chilton Jeep Manual (40602), the fluids should be changed every 30,000 miles. If the differential becomes fully submerged in water, it should be changed immediately after. For piece of mind, I decided to replace the fluids to get a baseline on the maintenance schedule. Hopefully, my XJ makes it another 30,000 miles!

The Chilton manual recommends SAE 80W-90 gear oil in each differential for standard driving. If the vehicle is used for towing, SAE 75W-140 should be used instead. If the vehicle has Trac-Lok limited slip differential, additional friction modifier should be added to the rear differential.

What's the Differential?

The first step is to to identify which differentials we are working with. I found this diagram from a CherokeeForum.com thread very helpful:



The following table summarizes the fluid capacities of each type of differential on the XJ:

Differential	Front/Rear	Capacity (Liters)
Dana 30	Front	1.2
Dana 35	Rear	1.66
Dana 44	Rear	1.89
Chrysler 8.25	Rear	2.0

My 1998 XJ Sport has a Dana 30 in the front and a Chrysler 8.25 in the rear.

Which fluid should I use?

I scoured the web for "the best differential fluid" and "top XJ differential fluid recommendations". In the end, I found that just about any 75W-90 GL5 gear oil will do. Since I was in the process of ordering Redline fluids for my transmission and transfer case, I decided to go with Red Line 57905 75W90 GL-5 Gear Oil.

Draining the Old Fluid

The easiest way to drain the old differential fluid is to remove the cover and let it fall out. Starting with the rear, jack up the vehicle under the differential and place jack stands under the frame. With the vehicle on jack stands, the differential will drop further, providing easier access to the top bolts of the cover.



Place an oil pan underneath the differential. Now, with an 1/2" socket wrench, remove all of the bolts on the outer edge of the cover, except the top center bolt! This prevents the cover from falling into the pan when prying it off.



Since I was removing the old bolts, I decided to purchase some grade 8 replacements. Each differential requires 10 of them. I used 5/16 x 1/2" and they fit just fine.



With a flat-head screwdriver, carefully pry off the differential cover. Use force, but try not to bend or scratch the mating surfaces. Once it's loose, the old fluid should begin draining out. Let all of the fluid out before undoing the final top middle bolt.



Now that the cover is off and the gears exposed, take this time to inspect everything. Look for pieces of metal or foreign objects anywhere inside the differential. Spray some brake cleaner all over the gears and inside of the cover. Carefully scrape the old RTV off of the mating surfaces of the differential and the cover. Wipe everything down with a clean rag or paper towels.



The same exact process is repeated for the front. The differential is much smaller, and I wasn't required to jack up the front. The bolts are already easily accessible.



While I had them off, I decided to a once over on the covers with Rustoleum spray. I cleaned as much gunk as I could off of the outside of the covers and sprayed away. Nothing fancy, and I don't expect it to hold up to much abuse.

Sticking the Covers Back On

Lay a strip of black RTV along the inside mating surface of the differential cover. I used Permatex 82180 Ultra Black Maximum RTV Gasket Maker. So far, it's held up great!



Now, line everything up and place the cover back on the differential. Twist the bolts back in by hand in a star formation. Then, go back over each of them with the socket wrench and tighten to 30 ft. lbs. of torque.



Again, the same exact process can be repeated for the front.



Before refilling, let the RTV dry. It shouldn't take too long, but I took this time to grab a bite for about an hour.

Removing the Plugs and Filling

The fill plug of the Chrysler 8.25 is just a rubber cap. It can by pried open with a flat-head screwdriver.



The Dana 30 requires a 3/8" square head attached to a socket wrench to remove. These can be extremely tight, so get ready to use some muscle.



Using a handy dandy Lubrimatic Fluid Pump, refill each differential until the fluid starts to overflow out of the fill hole. Since my Jeep has the Trac-Lok limited slip in the rear, I added 4 oz. of Red Line 80301 Limited Slip Friction Modifier to the Chrysler 8.25. The differentials will not be filled to the very top. It takes awhile to pump, so be patient.



Voila. Easy as that! Happy wrenching!