Diff Friction Modifiers?

[Severdog]

Planning to do front/rear diff and transfer case oil change. Researching this project was way more involved than I expected due to the huge amount of variability in trim levels/options. I have a plain old XLT PowerBoost with no 4A "shift on the fly." Can I assume that I do NOT want to add the limited slip friction modifier additive to the front diff?

99% sure the answer is "NO" but wanted to check with the hive mind here.

p.s. Also very surprised to see that the Amsoil equivalent 75W-85 gear lube is significantly less expensive than the motorcraft OEM fluid at $25/Q on amazon. Huh.

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[Pedaldude]

Unless you’re running a clutch plate style differential, the friction modifier is unnecessary.

Even for Torsen equipped diffs, some use it and some don’t.

If you have a regular open differential, you don’t need it.

If you have an electronic locking differential you don’t need it either.

The Ford gear oil is actually pretty good stuff and I’m curious how many miles are on your truck and how the stuff looks when you drain it out!

Good luck and let us know how it goes.

 

[WhiteLightningnshitshadow]

Do you have the locking diff or the limited slip diff? If you have the locking diff, you dont need modifier.

Im working through a crazy problem right now with my S197 LSD shuddering. It came on slowly, then I had a shop check it out and they added some modifier, then it was worse than ever. I just added more modifier and havent tested it out yet. Shits hopeless and I kinda wish it was an open diff at this point.

 

[Pedaldude]

How many miles? It might be the suspension bushings, a bearing or even the u-joint on the driveshaft.

 

[Babbage]

I used Amsoil, was dirty black at 2000 miles. Lubelocker makes nice gaskets with 3 layers of impregnated RTV.

I also have the 9.75 rear gear, Ford Racing makes a nice cover with magnetic drain... They have this also for super 8.8

Get all of the old RTV off, shiny clean before installing.

 

[Mosey]

You will need a vacuum extractor for the front diff. No way to remove the cover without significant work.

 

[Babbage]

You will need a vacuum extractor for the front diff. No way to remove the cover without significant work.

I had my front done at the ford dealer with my ford points.

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