Service Parts ID Tag in Glove Box
 

Inside the glove box door of my 99' Jimmy is a sticker thatreads the VIN and'SERVICE PARTS IDENTIFICATION Do Not Remove' then AJ1 ANL AN3 and 60some others like that. What is it? What is it for and how to decipher it?

In another post I read that the rear end gear ratio is listedsomewhere in the glove box. If so, I cannot find it.

Hereare the first 13 numbers/letters in theVINof mymy 99 Jimmy:
1GKDT13W8X254xxxx

RE: Service Parts ID Tag in Glove Box
 

The SPI label (also called RPO label) is what tells you all of the options that your truck came with.

Search for RPO and you should come up with the decoder or three.

RE: Service Parts ID Tag in Glove Box
 

Yeah, just google rpo decoder, and you'll most likely find what your looking for. The rpo codes are sort of the build recipie for your truck. The engine, tranny, color, interior trim package, etc. are all identified in those codes.
Gear ratio codes start with a "G" (except G80, which is locking diff). Most non ZR2 Blazers had 3.42 gears which is GU6 IIRC.

Oh yeah, and LMC has a nice vin decoder....
http://www.lmctruck.com/icatalog/cst/full.aspx?Page=11