2000 Z-71 lifted Diff change

[DesertRace21]

Ok, here is something I'm sure i will be criticized about.... I tow with my 2000 Z-71. We go up a nasty grade on our way out to desert races here in souther california. That is not the worst part. My truck has a lift and 315-70 16 tires on it. I am still running stock gearing and I have absolutely no problems towing.. in fact at the speeds i go.. the ratio seems ideal like the tires actually helped... BUT.... I smell gear oil bad after our last trip as if I had overheated it. I am about to change my fluid now that it is all burnt, but Id like to know what everybody uses. The factory synthetic seems to break down really bad. I was thinkin of running lucas in it because they sponser our race series and I get a good deal on it and it works in our race truck. I would just like to know what everybody recomends for fluid that will not break down so bad? I tow a ranger with tubing everywhere, four link rear and widened coil-oiver front, so I assume with trialer it is well over 6 thousand lbs. possibly a lot more. Any help would be greatly appreciated! Please let me know.

[budhayes3]

I use the GM synthetic 75-90, but my rear doesn't see the wear and tear yours does. If you have the G80 locker, you're gonna want to stay with a synthetic between 75to80w90. Or, you might want to think of upgrading your rear to handle the extra stress on it.