Did the 98 chevy blazer come with a locking rear diff or how can you tell if you have a locking diff

 

Pop open your glove box and look for the RPO code 'G80' on the RPO sticker.

It isn't a traditional locker. It is GM's gov-loc differential if you have code 'G80'.

 

I check the codes but i don't have no g80 or nothing like that so what does that mean what type of diff do i have, also do you know what size my axles are rear

 

That means you have an open diff. If you run a search, you should be able to find some posts on RPO codes. There should be a link in one of them to a site where you can plug all of your codes in and it will produce a list of installed options for you.

IIRC, you have a 7-5/8" ring gear which typically is the 'size' of the rear axle. If you mean something else, please explain further.

 

I wanted to put an arb locker in the back and they wanted the axle size I was just wondering if it would fit on my truck if not is there a type of locker that would fit. If there is none that would fit is there a way i can change the axle to a bigger size sorry for all the questions, i just wanted something for better offroad performance I heard a lot on bad stuff about open diffs.