HI!

truck: 1999 Ford F150 5.4L V8

how much friction modifer should be added to rear differential when changing gear lubricant?


service manual says 4 oz. for 8.8 & 9.75 inch rear axles and 8 oz. for 10.25 inch real axles.... how would you know what size rear axle you have?

thanks

 

Should say on the door sticker and on a tag on the cover. Be sure you have the limited slip before adding FM.

 

I've always put just one bottle of XL-3 modifier in everything that needed it. I think it's like a 6 or 8 ounce container.

 

You almost certainly have a 9.75". Does it look like this one, or this one?