Hi,
I bought some 3.73 gears and going to install in a couple weeks. I bought 80W-90 valvoline syn blend for the 500 mile break in oil. I was then considering using GM synth axle lube 75W90 afterwards (smells like grape juice part #89021677). Is that ok to use? I have 1.5qts left over from servicing the wife's envoy and the GM fluid was $25 a qt, so i figure i might as well use it. Also gonna add the GM slip additive for both changes, do i need to buy 2 bottles while at the dealer? I tried uploading an image of the fluids, but its not working.

Thanks,
James