I have a 77 f150 with 9" rear what gears is that? Like 3.5 or smtn?

 

Look for an axle code on the door sticker.

 

is it 2wd or 4wd if its 4wd it probly has 3.50 gears thats a common gear for them

 

Crawl under the truck to the rear end on one of the bolts that hold the diff in the housing you should find a metal tag. Next to the bolt you should see a 2 or a 3 the a space then possibly a 50 or 08 or 00. When you run them together will give you your ratio. Also if you find a letter L between that denotes a limited slip.