Or you can just jack the rear of the truck getting the back tires off the ground, then make a mark on the drive shaft and spin the drive shaft counting how many times the driveshaft goes round to get the rear tires go around one complete revolution.

 

look in glove box for code numbers[/align][/align]Rear End Ratio RPO Codes Here [/align][/align]GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)

HC4 -- AXLE REAR, 4.56 RATIO
[/align]

 

Welcome to the forum! Do you still have the options and price sticker that came on the window of your truck? Its printed on there.

 

I have a 2003 Chevy Silverado 1500 Z71. My question is: What feature of the VIN code tells me what my axle ratios are? I gave a local dealer my VIN code and he told me what my axle ratio is. I am looking for a replacement front axle differential and want to understand how to read the VIN codes. I understand the 4th through the 8th digits define features of the vehicle but I want to know what the code is for the axle ratios. Thanks!