have a 2008 F 150 4X4 with the 3.73 LS axle …..can't read the tag on the rear cover it's all rusted

drivers side door says Axle B6

I'm gonna change the gear oil and owners manual lists 2 size's of gears …..8.8/9.75 axle or 10.25 axle

buying the gear oil and don't want to buy too much …..which size do I have ? …..I have the friction modifier …..

thanks

 

The 8.8 rear cover is rectangle shaped with rounded corners. The 9.75 is shaped somewhere between a rectangle and triangle. The only trucks with a 10.25 have 7 lug wheels.

Normally, if you have a 4.6 you have a 8.8, if you have a 5.4 you have a 9.75.

 

thanks.....I thought I had included it's a 5.4L …..my mistake

6 lugs so the 9.75 @ 5.5 pints !

a "pint" in your general direction Sir

 

I refill mine with a piece of tygon tubing pushed onto the pointed cap so that I can hold the bottle up high and get all the fluid inside the diff. it's easier that way than using a suction gun. I pour the FM in one of the bottles.