I' want to get new gears from my truck but not sure of the size, 8.8 or 9.75
I have a F150 4x2 5.4L 2005 with a 3:73LS. I have 285-70-17 tires and was thinking of going to 4:11s.
My axle code is B6
any help would be great thanks.

 

I think its 8.8 in the front and the 9.75 in the rear, 34 long spline

 

It's a 2 wheel drive.

 

To confirm, crawl under and read the axle tag, there will be either a "975" or a "88" on it. All the "B6" on the door tells you is that it is in fact a 3.73 LS.

Going from 3.73 to 4.10 is not worth the expense, there won't be enough difference to matter much.