Just changed my Diff Oil 2 80/90- with MOLY-Slip @ 185000 Miles & I live in Winterpeg Manisnowba
That would have more meaning if you told us what axle it went into (8.5, 9.5, 10.5, or 11.5 ring gear) and, especially, whether or not you have Gov-Lock.
Yes I have a G80 according to the codes on my glove box.
Then you're in the same boat as I am--unhappy with any of my axle-lube choices, due to GM having vaguely-worded service bulletins and therefore incomplete information.
All I can say is that I crammed a 9.5" Gov-Lock axle under my '88 years ago. Had it apart for inspection, put in axle seals, filled it with Amsoil Severe Gear (75W-90?) and figured I was good-to-go. Within a couple months, the Gov-Lock quit working.
I changed fluid with Valvoline 80W-90 having no friction modifier in it; and it still didn't work. Eventually--not that long ago, just a couple months--I changed an axle shaft, refilled again with the Valvoline with no modifier. Seems like my Gov-Lock is coming back to life.
GM also has bulletins on NOT using synthetic gear lube in the various axles built before a certain date, unless you replace the silicone sealer used in production with actual gaskets. They say that synthetic gear lube destroys the silicone sealer, leading to leaks. I don't put a lot of faith in this--they tested ONE synthetic gear lube and had problems. Doesn't mean EVERY synthetic gear lube will interact with the silicone; and by now the OEM silicone may have been replaced by aftermarket silicone sealer.
I think it's 10 bolt 8.5 in, I will double check before ordering the gasket. Thank you for the info.
The Gov-Lock in the 7.5 and 8.5 versions are commonly referred to as "Gov-Bomb". Be careful. I guess the 9.5 and 10.5 versions have a better reputation.
It would be worth your time to pop the C-clips and slide the axles at least part-way out to inspect the bearing surfaces. Common for the axle shafts to be worn--sometimes severely--at the outer bearing area. Whether you pop in new axle seals is up to you. (Inspect for leaks before pulling the shafts out.)