REAR DIFF COVER

Rear differential covers are not only aesthetical pleasing, but they serve a very functional purpose; better cooling. With a larger capacity than stock, in this case 25% more, and cooling fins, after market diff covers help reduce heat in the rear diff, especially under stressful driving conditions, such as those encountered when off road. The added thickness also adds strength to the differential housing.

The Product
PML specialize in sand cast aluminum covers and offer one for the AAM 14 bolt rear diff as fitted to the H2. It is available from Trail Duty in cast finish, black powder coat and polished.

The product is well made and well finished and feels very solid. The gasket surface is very smooth and the aluminum is 3/8" thick around the gasket flange and 3/16" elsewhere. There is an easy to reach fill plug (level check) and easy to access drain plug. The stock drain plug is in the diff casing and leaves a small amount of oil in the bottom of the diff. This of course is where the sludge and other foreign matter gather and never get drained during routine service. The diff cover drain plug is at the very bottom of the diff, allowing all oil to be drained.

The drain plug is also magnetic, so that it catches any metal particles in the diff, a good way of also checking for potential issues. The drain and fill plugs are galvanized and come with a copper washer. The mounting bolts and washers are all stainless steel.

Full instructions were provided and should be followed, but here's my notes on the installation process.

Removal of stock cover
The complete job took 45 minutes and is very simple. As I discovered there is potential for a lot of dirt and mud to gather around the lip of the stock cover, so wash the whole area down very well before starting work. This reduces the potential for foreign matter entering the diff.

I didn't bother draining the oil out of the diff, I simply put a large container underneath and started loosening the bolts with a 1/2" socket. Once they were all loose ( 3 or 4 turns, I simply pulled the bottom of the diff cover away from the diff and the oil flowed out into the container. Do make sure the container is there from the beginning, as a small amount of oil will seep out as you loosen the bolts.

You need to "unhook" the bracket at the top, which kind of just pulls away, and then the cover just comes out underneath. Leave the container underneath as the oil will continue to drip out for a while.

Installation
The gasket surface of the diff needs to be cleaned up, mine had some rust on it and plenty of grime. I used a razor scraper and it all cam straight off. Be aware of anything falling into the diff, a lint free cloth can be used to cover the diff while you work. Once the surface is smooth and clean, use a degreaser to clean it. Before doing this it is a good idea to dab up any residual oil in the diff to ensure it doesn't run out over the now clean and degreased gasket surface.

The stock gasket appears to be of the reusable variety, however, I opted to go with RTV (red) high temp gasket maker. Double check the diff gasket surface for any oil and then mount the new diff cover, tightening bolts in the usual cross pattern. Once you have tightened all the bolts, go over and check them again, as the first ones to be tightened may become lose as others are tightened.

Finally, fill the diff with 75W-90 synthetic gear oil, remember it will now take more oil to fill now, also do make sure you have the drain plug installed first!

Overall, a very simple install that required minimal tools and was completed in 45 minutes.

Click on the pics below for larger images;


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