I've got a '98 ford(obviously) 4x4 with a 4.6, 5 speed and i wanna buy a posi and i don't know what size(9.75,9.0,8.8,etc.) of diff i got. I checked on the door jam one time and found out i have a 3.73 gear, non-limited slip rear. If anyone can tell what size my rear end is from that info or give me a link to another thread, that would be great!

 

im inclined to say you have an 8.8. count the bolts on the diff cover

 

11...i think.

 

the 9.75 has 12 bolts but i cant remember how many the 8.8 has, but if its not 12 then its an 8.8 haha

 

Great! That's exactly what i wanted ta hear I've got my eye on a posi for an 8.8! Thanks very much for the help

 

4.2 and 4.6=8.8
5.4=9.75
5.4 7lug=10.25

 

Thanks paralyzer! oh and my diff cover has 10 bolts, not 11, must've counted one twice lol

 

So would my axles be 28 spline or 31?

 

Axles are 31 spline with 7/8" cross pin.

 

Perfect, thanks for all your time and help everyone!

 

You realize dont you, that if you change the gears on the rear, if you ever want to use 4x4, you have to change the front too. Just making sure.

 

Unless i put different size tires on I'm actually not planning on changing ratio, i just want to upgrade to posi.
Thanks for the warning tho!