I just bought a 1992 K1500 Blazer. I was wondering if anyone knew what the available rear differentials were offered in that year (if any) and what the RPO code for those different rears would be. I have looked on the internet and found litte information. I suppose I could always jack it up and check to see if it is a posi or not and what ratio gears I have, but if anyone out there knows the codes Im curiouls to know what I have. I believe it to be a 3.42 open rear but when I drove it on gravel and gave it some gas both wheels spun an equal ammount which leads me to believe there may be an eaton in it....

 

I don't know if some of the RPO decoders that have been posted before would work for your application, but here is what I have found to be the ultimate RPO listing (188 pages of eye splitting RPO bliss) - Hope you have your reading glasses on!

Ultimate RPO List - 1.12Mb .pdf file

Just for your reference, an eaton wouldn't have been in there from the factory. GM used their own designed corporate gov-loc unit which works ok for on road and very light offroad, but when presented with some decent power and/or more involved off-roading, it would destroy itself.

A quick pop of the diff cover would answer any questions you have about your diff. If you don't have a good idea of the last servicing of the rear diff (or front), it wouldn't be a bad idea to change out that gear oil.

 

Thanx, I will have it memorized by tomorrow.