alright Iw as reading up if I change tire size that it might be wise to change my gear ratio. What is the best way to find out what my gearing is? Would the VIN run at a dealership be able to give me that information or does anyone else know where to check? I have a 99 chevy Blazer 2dr LS model. I believe it may have a tow package but I"m unsure. It does atleast have a towing hitch. if anyone knows It would be greatly appreciated.

 

Your RPO listing will give you the installed gear ratio in your truck. The RPO sticker is on the glove box door and consists of many 3 character codes.

Here's a list of the gear ratio's available and their associated RPO code:
GT4 Rear Axle: 3.73 Ratio
GT5 Rear Axle: 4.10 Ratio
GU4 Rear Axle: 3.08 Ratio
GU6 Rear Axle: 3.42 Ratio

 

by the looks of things I have the 3.42 anyone know where we can pick up new gear sets?

 

Has anyone changed there gear seats? To match up to the tires they need? It is looking like i need a 4.64. Anyone know where I can find one?

 

What size tire are you putting on?

 

Looking at 30's for now unless I get a lift. Be it either a suspension or body. Cause I'm already running rancho RSX on the front and rear.

 

You can use the 3.42 and 3.55 w/ the 30's for best fuel economy. 3.73, 3.91, and 4.11 for a daily driver and best overall performace (power & economy). 4.27 and 4.56 for towing and power.

Here is a formula you can use: new tire size/stock tire size = % of change X original gear ratio = new gear ratio.

This will get you right around where you need to be.

4wheel parts will have all you need.
website

 

That is where i was getting most of my numbers from. definately going to be checking them out more and more.