If i have a 89 Iroc is it the 7 1/2 or is it bigger? i dont want to buy the wrong 3:73's thanks.

 

you will also have to get a 3 series carrier for the 3.73s.

 

what do you mean, where do i buy that?

 

Do you have a 9-bolt, or a 10-bolt?

What gears are in it now?

 

i have the 10 bolt with i think the 2:73's i thnk

 

The differential is called the carrier. So you will have to get a 3 series posi unit (differential)

 

so that is madatory when you put in the new gears?

 

3.08 and numerically lower are a 2 series

3.23 and numerically higher are 3 series

so going from the 2.73 to 3.73 you will need the 3 series

 

Also the 7-1/2" and 7-5/8" are interchangable. They use the same carrier but as mentioned above, you'll need a 3 series carrier (posi) to swap to 3.73 gears because your current 2.73 gears are on a 2 series carrier.

There's also a very good chance your 1989 carrier is only 26 spline. Only a handfull in 1989 were 28 spline. They'll need to know that when you buy a new carrier. The only way to know for sure is to pull an axle and count the splines.

 

you can also use a shim or gears made to work on a 2 series carrier