I was thinking of changing my dif's, i know it takes 75/95w. the local parts store said I need to add locking dif additve to the oil. Is this true? Or B.S

 

BS or more likely ignorance. Refer to your owners manual.

 

It takes just about 4 qt of "SAE 75W-90 Synthetic Axle Lubricant". I've used Royal Purple which is available at most of the chain auto parts stores but there are a lot of good quality products available. Changed it myself the first time in about 1 1/2 hours but caught hell for the smell in the garage. The second time I had the guys at the local quick change place do it for $30 with me supplying an $8 hand pump and the fluid.

 

Sounds like BS to me.

 

The person you spoke with is a bit confused regarding additives needed for limited-slip vs. a locking differential.

What the person you spoke with was referencing is with traditional dino based lubes you need to use an additive for a limited slip differential, but not a locking differential.

Most modern synthetic gear lubes already contains the LSD additives they are referencing. All H3 are spec'd to use synthetic gear oil, but none of the H3 diffs are of the limited slip type, so the additive isn't an issue.

 

i just did mine saturday i use royal purple i didnt use a hand pump all i did get piece of clear hose about a foot and 1/2 and cut the top of the yellow cap so the hose fit tight put some hard wire inside the hose so the hose stay straigt to touch the bottom squeeze the bottle... maybe easy with pump but didnt have one. lol

 

A tip for changing gear oil: Place the new bottles of lube in a pan of hot water for a few minutes while you are draining the old lube out of the diffs. It will make it flow much easier.
You can also add a foot-long piece of fuel line onto the lube bottle tip and turn the whole bottle upside down next to the axle while you fill it thru the hose into the fill opening. Goes in real quick this way.

 

Great idea! The top of gear oil bottles will plug into a hose nicely as well . I hate that hand pump.

 

Thank you all for writing info, it was all helpful

 

I have some 75-110 Amsoil left over from my 1 ton dodge axle oil change that I want to use. Other then being a little heavier, is there any damage that can occur?Thanks in advance.