I found a retailer in my area that sells Amsoil. I changed the differential fluid in my IROC and put in Amsoil Series 2000 75W-90.
My question is - what is the difference between Series 2000 75W-90 and SAE 75W-90? The retailer didn't know.

 

five7kid where are you?

 

Sorry, haven't spent regular time on this forum for a couple of weeks.

The Series 2000 is their latest formulation. Slightly better viscosity characteristics at the extremes. Has the limited slip friction modifier in it.

The older, "regular" 75W90 would typically work in limited slip, but every once in awhile you'd need to put in the additive as well (5% or so). It has a slightly higher flash point (403 F) than the Series 2000 (388 F), if that's a concern to you.

I'm using the Series 2000 in all of my RWD vehicles, including open, clutch-type posi, and locker posi. No complaints from any of them.

 

Thanks for the info, kid.

What promtped me to change was I was getting a chattering noise from the rear under specific conditions. Cruising through my neigborhood at low speed, with foot off the accelerator, and bearing to the left, I'd hear it.

So after searching the board and finding numerous posts about whether or not to use the additive, and doing some other research on the web, decided to use Amsoil and not the posi additive (I have the BW 9 bolt).

It's been two weeks since and I have not been able to re-create the problem.

 

Did you do the figure 8's after changing the fluid?

 

Pretty close to figure eights. I live on a cul-de-sac which has about 40 yards of straight pavement before you have to turn around.

So I drove around the cul-de-sac, then out to the intersection, turning around the opposite way. After the fifth time doing this the neighbors were wondering what the heck was going on.