iflyfish

2000 Cherokee Sport.....After studying what looks to be a simple procedure, I plan to change my fluids since it hasn't been done since I got it 6+ years ago (second owner) and despite searching the forum, I can't seem to pinpoint information regarding the need for friction modifier. Information I found was somewhat lacking as to whether I actually need it. The rear is a Chrysler 8.25, front is a D30. I understand the D30 is an open diff and from what I see on my build sheet, I do not have limited slip in the rear but I won't know for sure until I pop the cover and see what I've got in there. I seem to vaguely recall and am not quite sure that when up on a jack once, when I rotated one rear wheel, the other side turned the opposite direction and from what I understand that indicates no limited slip. I'm venturing into uncharted territory here and I'm thinking I should have it on hand should I open it up and see limited slip...but do I really need it? Also can anyone recommend good quality fluids to use?

wahoo

When I did mine I used Lucas oil full synthetic, its a little pricey but good stuff. Its real easy to do, just let the silicone set up a little before you put it back together.

1976Mustang

You only need a friction modder if you have a limited slip. good way to test what diff you have:
1. Lift the rear wheels into the air (front tries blocked)
2. With the tranny in neutral, spin one of the wheels. If the other wheel spins in the opposite direction, it's an Open diff. If it spins the same direction it's a limited.

ZINGGG

A lot of gear oils have a friction modifier already in them. From what I saw, there really wasn't much of a difference in price from those that had it to those that didn't. So I would pick up a brand that already has that since it won't hurt anything if you don't have limited slip.

I am a Mobile 1 believer. But brand is really all preference.