It calls for SAE 80 oil.
Would a 75w90 Synthetic be ok?

 

abmobil,
This is my first reply. I have been reading all the valuble data on this forum, especially about oils (changing intervals, petro vs. synthetics., break ins, etc.). I am planning on purchasing a Rancher 420 next month and also wondered if you can use a 75w90 gear oil in the rear end. I know I use Lucas synthetic gear oil in my 2000 S-10 ZR2 and the transfer case oil in all the diffs and transfer cases and swear by it. At a 140k miles on my truck I use the synthetic oil stabilizer in the engine as well. Can anyone answer if Lucas synthetic would be safe in the rear end of an ATV? I wish I could be more help with your question abmobil; I hope someone who knows there stuff will answer this because I would love to use the Lucas (or something else) over the stock stuff. Not that it's bad, I just trust Lucas!

 

I have been running Maxima synthetic 75W90 in my 00 Rancher for several years, and that is what I just put in my 07. Do change out your diff and rear end fluids more often than every 2 years like the owner's manual suggests!
http://www.maximausa.com/products/ge...thgearlube.asp

It calls for "hypoid" oil, so run something that says hypoid or is GL5.

 

Some gear oil discissions: http://forums.atvconnection.com/mess...did/511416.cfm

http://forums.atvconnection.com/mess...did/511855.cfm