I've got a 98 blazer 4x4 auto that im buying a complete rearend for. I keep getting asked is it a 7 5/8 " or 8 1/2 " gear size ? I know it is a 3.42 ratio (GU6). But how do I tell if it is either gear size ? I've checked all RPO' s in glove box and they don't tell which size.

 

Most likely you have the 7 and 5/8" rear. ZR2's got the 8.5" rear, not many of us non ZR2's got 'em.

Here's a quick visual:



8.5" rear has a more round diff cover. 7.5 and 7.625 (same externally) have more of an oval cover.

 

ZR2s did not come with 3.42s, so you have the 7.625 diff.

 

thanks