Hey folks, I am wanting to upgrade my differential from an open axle to a limited slip. The vehicle is a 98 GMC sonoma with a 4.3 V6 and heavy duty suspension.It is 2wd and a 3.08 axle ratio. I called gmc and they told me it is a 8.5 rearend. How do I find out for sure what size it is and also how many splines I have.I have never done this before so I am unsure of where to start.Thanks.  

The Sonomas were the S10 of GMC line wasn't it? That would make it a 7.5" rear and most likly 28 spline. I have a gov lock version for 1 of those right on the shelf and it's for sale.  

Except for maybe a 4x4, i didn't think they ever put the 8.5" 10-bolt in the small trucks. I'd take a measuring tape to the center section and see what the height is.  

Someone told me there are numbers stamped on the axle and that a dealer could tell you what you have by those numbers. I looked and haven't found any. Also the sonoma is the gmc version of the S10.I can't afford anything at this time, but am gathering all the info that I can and also compiling a parts list of what I want to do and it will be probably Feb or March next year that I can do the upgrades.Right now I am replacing the wear and tear items.Thanks for the replies.