Gear Oils

I want to go ahead and change out the oils in my diffs and transfer case. I understand the transfer case gets tranny fluid and the diffs get gear oil. The manual shows 2 different types. 75W-90 for the front and 80W-90 for the rear. Can I put 80W-90 in the front and be fine? I cannot remember what I did last time I changed them out. Also can someone point out where the heck the fill port is on the front diff? I cannot find it.

 

Front center almost. Up in there... I used the same Fluid for the front/center/rear. It’s runs SO good I enjoy every minute of it...

 

I looked in my manual and it says gear oil in transfer case if you have a manual or 4cyl but use Dexron II if 6cyl with auto. I wonder why?

 

When I change the oil in the front and rear differentials I don’t get too concerned about the weight as long as it is GL-5 oil. I would have no problem using 80W-90 in the front and rear diff.

 

I don't know if the transfer cases on manuals and autos are the same, but the biggest reason that you run Dexron in the auto transfer case is migration. If a seal goes out or leaks between the case and trans, you don't want gear oil mixing with the ATF. My guess is that there is a difference in the make up of the auto transfer case also so that the lubrication is sufficient with the ATF

 

Thanks all. Now does anyone know where that fill port is on the front diff? For the life of me, I cannot find it.

 

It’s on the front of the diff.

 

Thanks Just, I finally found it. Looks like the skid plate will have to come off. Boy that was nicely hidden.

 

For what it is worth I have been putting 75W-140 Royal Purple gear oil in everything (there is no AT in my 4Runner). The additive package works a charm in the R150F 5 speed when its cold and is providing a quiet clicking in my Grizzly Locker. I haven't replaced the front axle lubrication yet but I would expect the ADD will like it!