Friction modifier in conventional differential.

Cougar Community Classic Cougar Maintenance Restoration and Repair
1

The differential tag on my 68 XR-7 reads WCZ-F1, which is a conventional type. I want to change the oil in it, but I am unsure if I am supposed to add friction modifier to it?

The 1968 Cougar shop manual I have states conventional differentials take 4oz of the modifier, yet the text on the modifier state it is for limited slip type differentials.


Thanks again,
CWatson

This is what was recommended to me by one of my parts sources:
https://www.amazon.com/Genuine-Ford-XY-80W90-QL-Premium-Lubricant/dp/B000NU1D3U/ref=pd_lpo_2?pd_rd_i=B000NU1D3U&psc=1

Friction modifier if required:
https://www.amazon.com/Ford-XL-3-Friction-Modifier-Additive/dp/B000NU5LP6/ref=pd_bxgy_img_1/141-3803677-3723954?pd_rd_w=3YKKu&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=WVV4XFGF14PHHJS7R8JQ&pd_rd_r=715ac265-4b9d-4cbf-b9e5-54cf7088c5b1&pd_rd_wg=N2BG3&pd_rd_i=B000NU5LP6&psc=1

2

Friction modifier is only used in Traction Lock differentials. If you have a standard rear, or a Detroit Locker, use only differential grease.

3

Thanks for the info.

Strange the incorrect info has gone uncorrected for so many years.

CWatson

4

Once a book is printed you are stuck with the mistakes forever.

5

Wow, just checked mine; there it is, big as life. On the wrong line for over 54 years…