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Changing rear differential fluid in a AAM axle So to start off this is my first article, So please bear with me. First I did was locate the fluid I wanted to use in my differential. seeings how i didn't have a posi or limited slip, Any dino gear oil of the correct GL-5 rating would suffice. I picked up a 2 gallon jug of travelers 80w-90 gear lube that is GL-5 rated. http://www.tractorsupply.com/tsc/product/traveller-multi-purpose-gear-oil-80w-90-2-gal?cm_vc=-10005 I also picked up 2 cans of brake cleaner spray. Side note: 15w-40 oil was on sale for 9.00 a gallon. i got 6. After getting home, I parked on level ground as you always should when working on the rear differential. Tools need was my trusty impact drill with a 13mm socket. The gasket on the differential is a reusable one so take care when removing. i started with the lower bolts and worked back and forth across the cover. Eventually the fluid started leaking out into my drain bucket. After letting the fluid drain for a few min. I removed the remaining bolts. Inspected the fill bolt and magnet on it. It was surprisingly clean. The fluid color wasn't as bad as I thought it might be being I had 38K miles on it and the manual states ever 30K miles. I sprayed the brake cleaner in and let it drain kinda flushing out the old oil and metal residue. Inspected the backlash and bearings. Nothing was of a concern so I placed the gasket on the cover with two bolts going through to help hold it in place. Reinstalled the cover by starting each bold BY HAND first. then my impact tightened things up. Removed the fill bolt with a standard 1/4 inch drive ratchet and set the pump in the jug and started filling the differential. after 4 quarts mine wasn't spilling out the hole, so about another 1/4-1/2 quart went in. I don't think it'll hurt anything. Replaced the fill bolt and cleaned up the tools. Drive it around the block, check for leaks. all is fine today. The front differential should be similar you just have to jack the truck up and let the axle drop so you have access to the cover bolts behind the track bar and steering linkage. Read my other article about the fluid change on the T-case. Total time about 15 min. Pumping the fluid back in takes the longest. questions? comments?