Hello,Just got my 1997 4 door 4x4 blazer lifted 6 inches. it has 3.42 gears. looking to up diff to 4.10 or 4.56 to regain power lost with the 33x12.50 tires. Can any one tell if there is a way to identify the front and rearring gear size and rear axle spline count without tearing everything apart? Thanks

 

I believe that the front is a 7.2", and most of the 4 door Blazers have a 7.5" rear, although a select few came with the heavier 8.5/8.6. If you Google, you'll see lots of images on identifying the different GM axles.

 

Thanks for that info. I have been told that the 2wd came with the 7.5 and the 4x4 came with a 7.625. I have been trying to verify this without having to disassemble the rear.

 

/Check the codes in your glove box. If you have “GU6” then it’s a 8.5”

 

I believe (and I could be wrong) that they all changed to 7-5/8 after a certain year. I also believe that the gearsets are interchangeable between the two.

Here are the gear listings from Randy's.