I tow on a pretty regular basis usually about 10,000 lbs. I changed my gear oil to royal purple 75-90 about 4 months ago,but that seems kind of thin from what I have read here.What I need to know is what weight gear oil I should use. Price is not a problem so any help would be appreciated.

 

You ought to move up to an 85W-140. Stick with a synthetic, they hold up a lot better to the heat towing heavy will generate. Royal Purple is good stuff, no reason you shouldn't buy their oil in the heavier weight.

 

Only jumping in cause I, too, have a question on gear oils, for the NP205. 85/140 in the Lucas is what I am leaning towards, but FSM recommends 80/140. The Lucas is much thicker in coonsistency, as you all know. Which of the 2 do you prefer? Is there a difference? Keep in mind my CA temps. Currently I have ATF #4 in there.

 

If you're not working it hard in 4wd you really don't need such a thick lube in there. A good 80W-90 would be better because it will flow better when the transfer case is cool.

Same reasoning goes for rears. A truck like mine that just loafs around town empty has no need for 85W-140, the thick lube will actually not protect as well because it never gets warmed up and can't flow as well. An 80W-90 is a better choice in that situation due to better cold flow.

 

what about the tranny?? I am going to change my fluids soon. Just wondering

Jon

 

5W-30 synthetic or one of the light trans lubes like Redline MTL or Royal Purple Synchromax. A synthetic ATF will work, too.

 

Thanks again, Guru.