So me and my dad never really worked on rear ends n such, all we know is that the old cars with posi has 4:11 and 3:73 gears i got a 2000 mustang and we want to make it posi hes wondering if we put 4:11 gears or something in it will it make it posi? i thought i had a open diff so i thought i needed t-loc or something... but would gears make it posi? thanks in advance

 

This is the t-loc which will give your car "posi" allowing both wheels to spin


These are gears which will change your acceleration rate only.

 

I am not sure I fully understand your question.

But your car (2000 V6 mustang?) has a 7.5" rear axle and it comes from the factory with an open carrier (or open differential as you call it).

Gears alone will not make it an LSD (posi/tlok etc.) you need a t-lok (or any LSD for that matter) to apply traction to both rear wheels at the same time.

Useful links:

https://mustangforums.com/forum/v6-1...-end-info.html

http://3.7mustang.com/vb/f6/everythi...aps-etc-29525/