I found a website that lists all the RPO codes and after I went threw all the codes I know my blazer has the 3.42 gears.( not the ones I was hoping for) I still have no idea what size it is. Whether it is a 7.5 or 8.5 rear any info on how to tell would be great

 

What's the specs on your truck? Chances are its a 7.5 unless you have a ZR2

 

Its a 97 4 door 4x4 and does not have the g80 another bummer

 

also the axle tubes for the 7.5 are the same size from end to end. the axle tubes for the 8.5 get larger just before the pumpkin.

 

The chances of 4 door having a g80 rearend are as lucky that hair will regrow on the top of my head or my psychotic neighbor will move sometime soon.

 

I have 3:73s and a G80

 

Yeah but did the vehicle come with them gears or did you install them?

 

Surprisingly they are factory! I even managed to get the full skidplate option

 

I had all 3 of those options on my 4 door as well. Thing was a beast for what it was.

 

The only way to get the 8.5 10 bolt in a 4 door Blazer is an axle swap from a ZR2. If you go this route, it's pretty easy to do the rear axle. I did mine in about 2 hours by myself in the driveway. Swaping the front diff to keep matching gears is a lot more painful, but possible to do with normal hand tools. My truck came with 3.42 gears too, and I swapped in a ZR2 axle to get the 3.73 gears, wider stance, and the G80 locker.