GM-GMC: rear end, ring and pinion gears, gmc sierra

Question
i need a new rear end in my truck and i need to know the gear ratio. itis a 1996 gmc sierra step side i think it is a 5.6 or 5.7 .  

Answer
There should be a sticker in the glove box or under the hood of your GMC that lists the Regular Production Option (RPO) codes.  You need to check that sticker to see if your axle code is listed.  If there is a code for the rear axle, a dealer should be able to tell you the ratio.

The most direct way to check the ratio is to remove the rear axle cover and count the number of teeth on the ring and pinion gears.  Thi involves draining the gear lube and will require a new gasket and gear lube.