has anyone changed their differential fluid? and if so, where did you purchase your friction modifier? thanks

 

Royal purple 75w140 gear oil already has friction modifier added. It's about 60$ for the oil. If you plan to get 3 quarts

 

If you use some other brand of 75w140 gear oil, you can get the friction modifier from Ford.

 

If you have a LS, use the Ford stuff no matter what the lube you use. The clutch packs are very picky about LS additive and many have had to go back and add the Ford stuff after the fact and it is much harder to do.

I ordered all my stuff from Amazon. I used Lucas 75w-140 Synthetic and the Ford XL3 stuff.
About $50 shipped (3 qts fluid and 1 bottle FM) using the links above.

 

Or just take it to the dealer and pay $80.

 

What dealer does it for that? Heck, around here, $80 is just the labor cost, plus another $70 for the fluid and FM.

 

I use the friction modifier at O'rielys, - it's the exact same stuff as Ford. In fact I haven't seen a different type yet. Think it's made by trans tune or something ? Can't recall, but they usually carry it there.