I would like to change my rear diff. fluid over to amsoil synthetic. I see there are two types offered to choose from one is sae 75w-90 synthetic and the second is series 2000 sae 75w-90 which one of these do I want for the rear end? The only difference I see in reading about each is the price. Also will the amsoil sae 80w-90 synthetic be ok for the front diff.?

I believe there are more additives and closer match to grape juice in the 2000 ser.

???? What size tool does it take to get the drain and fill plug out? (I tryed 1/2" & 3/8" and no go (too small) looks like it's some kind of star allen wrench.

I believe that Amsoil has a new HD differential oil out which may be better for our diffs. I have the 2000 in my truck (90/140, as I tow), but next change, I will switch.

Tom,
I just orderd Amsoil for mine. The new stuff is called Sever Gear.

???? What size tool does it take to get the drain and fill plug out? (I tryed 1/2" & 3/8" and no go (too small) looks like it's some kind of star allen wrench.

I just used an allen wrench.

flivver, What size allen?

flivver, What size allen?
Don't remember. I just tried several until I found one that fit.

Hmm, the 3/8" ratchet fit correctly on my drain. Fill was a regular socket.

Hmm, the 3/8" ratchet fit correctly on my drain. Fill was a regular socket.
ditto:grd:

Mine also was a 3/8 for the drain plug and regular wrench for the fill. Really easy to change, love that drain plug instead of having to pull the cover.

Just did fluid change yesterday in rear diff. Drain plug was a 3/8 drive and fill plug was a standard bolt 5/8 if I remember correctly.