ok thanks so just keep stock gears with 31s? And im gonna get a bored throttle body will it help with the horsepower i loose?

Do you know for sure that you have 3.73 gears? What rear end RPO do you have? The 3.73 would be RPO GT4. If your RPO is GU6 then you have 3.42 gears.

ill check on that and how can you tell the difference between RPO'S?

Look in your glove box. There will be a list in there. They normally are in alphabetical order a-z. You may be able to find a website that can give you an RPO printout from your VIN number that will detail all the factory options and equipment. Those are handy to have too.

Ok thanks

Found out my truck has 3.42 gears and a locking rear axle. So when I get 31s ill be puting 3.73 gears in it.

Would it be better to just buy a zr2 rear end to save me the money of puting the gears in?

Swaping the rear axle would be a lot cheaper that swapping gears. You can get an axle for $100-$200, and it can be done in the driveway with hand tools. If you want to upgrade to a ZR2 axle this would be a good opportunity too.

A zr2 rear axle is like 3" wider than a normal 4x4 axle, which I think is like 3" wider than a 2wd axle. You really should just start one thread and stick to it, cuz you've got like 4 different threads going about all the same things, but you only mention its 2wd in 1 or 2 of them. It helps people provide more accurate info when you give detailed info on your ride. If you wanna gain 6 inches of width for just the rear axle, swap the zr2 axle in, but they have a 8.6" diff, and its longer then a stock 7.5" diff, so if your rocking a 2 door or 4, I can't remember, but if its 2 door, grab the driveshaft from whatever zr2 blazer you take the axle from. If you take it from a truck, you'll have to have your driveshaft shortened a couple inches.

What if I get a 2 doors 4wd rear axle would it be 3.73 ratio or not?