how do you know which axle you have? i went to 2 different stores and was asked, ended up taking a gasket out to the truck, sliding underneath and holding it up to the rear cover to see if the bolts line up, it was the right on, but neither the owners manual (useless, unless your looking for what fuse to pull to do away with the D.R.L.) or my haynes book says anything about 2 axle types, is it based on ratio? i found out i have the 3.42's , wish it was the 3.73's but i guess i'll get better highway milage with the 3.42's

 

I just compared the bolt pattern with the photo they have online. There is a major difference. Also,

"rear differential fluid 80W-90 GL, 4 pints (2 quarts)"