1999 GMC Suburban "weight oil goes front axle" Questions

Front drive axke What lube goes into the front axle of a 99 GMC Suburban, 4WD 85w 90 weight gear oil.

oil that could have attributed to the failure of the reverse. Any Ideas?? I think the problem is most likely in the shift linkage, manyually shift it into reverse at the trans (bypass shifter) and see

...oil will run out of the hole for the axle if you haven't drained it, so have a pan that will hold about 3 quarts under it. remove the battery and battery carrier platform. Support the engine. Remove ...