Oh ya missed this, count teeth on the ring and pinion and do some division.

 

yes but when i had someone paced me i was going 70. i order this 4.10 gear package http://www.texas-speed.com/shop/item...mid=54&catid=6
is there anything else might need.

 

Ok then at one time your car had a gear in it, and it was adjusted for it, and then that rear was dropped in, but it was not re-adjusted. Your speedo is going to be even more off if you put in different gears again. Also make sure if you have a 3 series or 2 series carrier, I believe the ring is different on them. Find someone reputable to put them in too. 4.10 is alot of gear, hope you enjoy shifting!

 

if its a stock rear, than it isn't 2.73's...

 

+1. I had to do the same thing when I got mine. Luckily my stepdad is a paint and body man and can do fiberglass. After we did that about 2 weeks later my window motor went out lol. But yeah your gonna have to reglass all the door where the pop rivets are.

 

Instead of counting teeth, just look on the end of your pinion gear. There should be two numbers. Just divide them into each other and you will get the ratio that you have.