rear diff ratio
 

my trucks an 01 extcab 4x4 with a 4.8 does anyone know what the diff gear ratio would be

Look in the glove box at the RPO sticker. Look at the "G" area - it is in alphabetical order. Here is what they mean...

Rear Axle Ratio
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

thanks, i had those numbers but didn't know were to look

Head over to www.compnine.com/vid.php with your VIN to decode all of your RPO codes from that glove blox sticker. You'll be surprised what you find.