hohokom

When the manual states you should use 75/90 for regular driving and 75/140 for towing, what do they mean by towing? Is this if you tow everyday, or if you do tow a couple of times a month, and that is just a small camping trailer.
I just want to put the right fluid in my diffs.

MoridinTX

The way I see it I always run 75/140 in the rear. The rear takes the most abuse, daily driving, towing sometimes etc. When you drain the front and rear the rear oil always looks worse.

I also have to put up with the South Texas heat... I have never had a problem in any of my vehicles running a heaver oil.

Also, if you have a lot of hills/steep grades to climb, I can see the heaver oil being better. My 2c

bostonMA

I think that your gear ratio and tire size and tow wt are all factors. Along with the towing issue, there is the question (though not for stock talk) if everyone running bigger tires should be using a heavier wt gear oil as well.

I am curious as to how gear ration vs. tire size affects oil wt. as well. My thought is that a 3.21 on 32" tires will heat up faster than a 4.10 on 32" tires as there is more stress on the gears at all times.

However, this thought contradicts certain postings that have stated the need to run higher wt. after they have re-geared.

Jedi Knight

I put 75W-90 in my diffs. I was thinking about though, even if you don't tow but offroad a lot should you put in 75W-140?

Adam3612

In my manual it says to use 80W90 in the front and rear axles not 75W90, and if towing it says to use 75W140

ronjenx

You can't go wrong with 75W140 synthetic in the rear. You'll be covered for all situations.

Adam3612

It's days like this that I wish I lived in your guys' neck of the woods! All the good quality products like Royal Purple and Mobil 1 gear lubes are readily available at your local auto parts store. Here in Canada its like trying to find a needle in a haystack and if by chance you do find these products you better be prepared to get reamed at the cash register. You'd think this place was a third world country or something.

RevyJKU08

I know everytime I have to actually order Royal Purple 75W90 weight gear oil and even 303 fabric protector & UV protectant...they bring in special order for me.

I still get hit hard for the cost of the lubricants...but what they are asking retail is insane and told the manager that I would not pay those stupid prices so, he gives me at min 40% discount on all products for being a loyal customer.

Dex1

I have allways used Valvolene full synthetic products, motor oil and gear lube, 75/90 front, 75/140 rear..
Never had a problem...

Adam3612

I cant find a damn thing around here for gear oil except Royal Purple which is like $18 a litre. I've worked with a couple of people who are engineers for Exxon and Imperial and they say they would never put RP near their personal vehicles even if it was given to them. Anyone down south wanna buy some Mobil 1 75W90 and ship it down to me? haha