IRS Friction Modifier Amount

[VAHokie]

Hey guys, instructions say to put 3-3.5 of the friction modifier in the diff but looking at Ford workshop manual it states 4 oz. What is everyone doing?

[Gordon Levy]

4oz.

[edwardb]

Looks like Ford shows a different amount of friction modifier depending on Mustang model. 2.3L/3.7L/5.0L = 4.0 oz. 5.2L V8 GT350 = 3.25 oz. I've always used the full 4.0 oz bottle of Motorcraft Additive Friction Modifier XL-3, PN EST-M2C118-A.

[VAHokie]

Thanks, Gordon and Paul. 4 it is.

[Traveller]

I just used 3.5 based on the following from Ford tech support for the IRS rear diff:

https://thefactoryfiveforum.com/attachment.php?attachmentid=114632&d=1569019833