Here is a UOA from my 2001 GMC Sierra 1500 Z-71 with ~96,500 total miles on the truck, and 43,500 miles on the Amsoil SVG 75W-90 oil. When I changed the gear oil with Amsoil, I bought 6 quarts at the same time with the same batch number on the bottle. Before the Amsoil both differentials were filled with Mobil-1 75W-90 oil. The rear (G-80) UOA shows a high TAN. It also shows higher Phosphorus and lower viscosity than the front UOA. This may be because after about 20k miles the rear end started to chatter, so I put a bottle of GM Limited Slip additive in the rear differential. The LS additive must be mostly Phosphorus. The front has higher iron, but that ppm is for 1.9 quarts where the rear ppm is for 2.5 quarts.
There are several pictures attached. You can see a lot of gray stuff on the rear cover magnet. That may have cut down on the wear metals present in the UOA. You can also see several high power magnets on the outside of the cover in one picture. I was surprised that there was no metal clinging to the inside of the cover where the super magnets were placed. The inside rear cover also shows signs of rust. I don't remember the rust being there the last time I had the cover off when I filled it with Amsoil. Could the high TAN have cause the rear cover to rust and the teeth to pit making them look dull. The gear teeth mating surface looked dull - almost like it had been bead blasted with very fine grit. I can't remember seeing a rear ring with a dull surface. I think most of them are shiny. I can't remember if the front drain plug had a magnet attached.
Compare my UOA with the VOA for the Amsoil SVG:
Amsoil SVG VOA
Pictures are taken with a cell phone camera, so the quality is poor; I forgot my digital camera when I changed the oil. I tried using a Harbor Freight LED flashlight to illuminate the gear in some of the pictures.
Rear UOA
Front UOA
Inside cover with factory magnet
close-up of factory magnet
Outside cover showing 8 super magnets
Pictures of the inside
I poured the used gear oil in a milk jug and then waited 2 weeks for it to settle before pouring it into a recycle container. These pictures show what might be clutch material that settled out on the bottom of the jug.
Front differential (nothing to see)
Eneos 75W-90 gear oil looked clear
Amsoil SVG 75W-90 oil looked amber
There are several pictures attached. You can see a lot of gray stuff on the rear cover magnet. That may have cut down on the wear metals present in the UOA. You can also see several high power magnets on the outside of the cover in one picture. I was surprised that there was no metal clinging to the inside of the cover where the super magnets were placed. The inside rear cover also shows signs of rust. I don't remember the rust being there the last time I had the cover off when I filled it with Amsoil. Could the high TAN have cause the rear cover to rust and the teeth to pit making them look dull. The gear teeth mating surface looked dull - almost like it had been bead blasted with very fine grit. I can't remember seeing a rear ring with a dull surface. I think most of them are shiny. I can't remember if the front drain plug had a magnet attached.
Compare my UOA with the VOA for the Amsoil SVG:
Amsoil SVG VOA
Pictures are taken with a cell phone camera, so the quality is poor; I forgot my digital camera when I changed the oil. I tried using a Harbor Freight LED flashlight to illuminate the gear in some of the pictures.
Rear UOA
Front UOA
Inside cover with factory magnet
close-up of factory magnet
Outside cover showing 8 super magnets
Pictures of the inside
I poured the used gear oil in a milk jug and then waited 2 weeks for it to settle before pouring it into a recycle container. These pictures show what might be clutch material that settled out on the bottom of the jug.
Front differential (nothing to see)
Eneos 75W-90 gear oil looked clear
Amsoil SVG 75W-90 oil looked amber
