i have a 2006 f150 FX4 with 106,000 miles on it.
i want to upgrade the differential cover but i dont know what size my cover is or axle size it is.
whats the best way to find out? do i just go by how many bolts there are?
i just dont want to buy the wrong one.

 

If I remember right the 9.75" has twelve bolts and the 8.8" has ten. If your truck has the 5.4L engine it should be the 9.75".

 

9.75 inch cover

 

8.8 inch axle cover

 

yes it has the 5.4L