Diff Fluid Question -Clutch Type Posi

[mda440]

I'm rebuilding my rear end, and am installing a clutch type sure grip, it was open before. I'm wondering what fluid and additive I need. I've been told everythng from 75w-140 to striaght up 80 weight gear oil. What is the proper fluid and will any posi additive work? Is synthteic a good idea and does it require and additive? Thanks for any help.

 

[66dartman]

You will need an additive for a clutch type limited slip diff. There are many brands available. As far as the oil goes, the synthetic 75-90 is good but a little pricey. It is not as thick as the standard gear oil cold, so there is a little less resistance and that translates into a little more speed!

 

[dgc333]

I use Mobil 1 75W-90 in the diffs of all of my vehicles. It's a highly regarded synthetic. I use whatever friction modifier that the part store has and have not ever had any issues.

 

[rumblefish360]

I just changed out my fluid in the Magnums 9-1/4. Auto zone has a additive that worked just fine. Also Mobil synth was used without a hitch.