diff friction modifier

[So Make Like]

is it really that big a deal to add the friction modifier prior to filling up oil in a diff? if it is, why? what is the difference between that and adding it after? some say it makes the difference, others say it doesn't. why is that? someone shed some light on this; as i don't see the obvious problem that some of you make it seem to be. please and thank you.

[jr_ss]

That depends solely on what diff you have and who made it. A VLSD isn't going to gain anything by adding friction modifier because internally, it's a sealed unit. Typically, friction modifiers are run to quiet down a diff. They allow the mechanical parts to "slide" against one another easier. If you don't mind some chatter, which is common in all clutch-type LSDs then don't worry about it. Your best bet, stick with the recommended fluid weight the manufacturer suggests to run with that differential. Call the manufacturer and ask them what they say and if they recommend friction modifier to be run with their diff.

[derass]

Some clutch type differential chatter very badly without any modifier. This excessive chatter is likely damaging to the clutch plates as they skip against each other violently. Gear oil from Kaaz/Nismo/Cusco have modifier in them as well as some cheap gear oils, as they are described as for use with LSD.

[So Make Like]

i have a tomei 2-way. as for the additive, i understand what it is, what it does and why it is or isn't used. but thank you for the input, regardless. i was wondering specifically about why some people go out of their way to tell people to add the friction modifier before the oil and if it makes a difference over adding it after the oil.

[jr_ss]

If the oil that's supplied with the diff already contains it, you don't need to add more, so it shouldn't matter. You'd want to add it to your existing diff oil if you were to add it. I've read about 5oz of it to your oil. I wouldn't run just friction modifier in my diff.

[godsmack]

Just add it whenever you want, and after you add it spin you rear tires before you lower the car to help mix it together.

[derass]

I mix the additive into the first quart of gear oil, then pump into diff. This way the additive is mixed somewhat evenly into the gear oil, certainly better than adding the stuff first before the oil.

1 bottle of additive per change.

[So Make Like]

alright, thanks guys! and yeah i'm using pennzoil 80w90. doesn't come pre-mixed with additive. i'll just pump in the small bottle of ford friction modifier since the gear oil is still freshly changed.

[codyace]

Ford Friction Modifier works great, and can be found at WalMart, or any Ford Dealer. Cheap too, 8 or 10 bucks a tube.

Parts shelf stuff works ok, but for the same cost the FOrd stuff is the best.

The best stuff IMO is the Spicer brand stuff,but that's going to be found at trucker places only.