Friction modifier or not?
Friction modifier or not?
Just got the gears swapped and installed a Trac Loc but wondering if I need the friction modifier? I'm using the full synthetic 75/85w motorcraft gear oil and have heard that friction modifier isn't needed when using full synthetic. Thought I would get some opinions...
What say you???
What say you???
5 Year Member
Joined: Jul 2018
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It is still required with a clutch based LSD like the trac-loc. Some synthetic diff fluids advertise having friction modifier already added, usually by an LS on the bottle for limited slip, however its been my experience you still need some additional FM added otherwise you'll get chatter.
5 Year Member
Joined: Oct 2011
Posts: 4,031
Likes: 1,087
It is still required with a clutch based LSD like the trac-loc. Some synthetic diff fluids advertise having friction modifier already added, usually by an LS on the bottle for limited slip, however its been my experience you still need some additional FM added otherwise you'll get chatter.
Cost isn't an issue, I will add some before I drive it again. I've driven it for about 35-40 miles with no noticable chatter but I guess better to have and not need vs need and not have.
