need info on differential.

How can I find out what is the gear ratio for the differential to my 2000 astro.

Locate the RPO label for the vehicle. It should be on the rear panel of the passenger door. Axle codes generally begin with a "G". For example, "G80" usually indicates a locking or limited slip axle. "GT4" for a 2000 Astro is a 3.73:1 axle ratio. "GU6" should be 3.42:1.

You other options are to dive under the vehicle, clean off the right rear axle tube, and read the stamped markings, or remove the rear center housing cover and start counting gear teeth.

OK, checked it out, my van has a GU5 not a GU6. Is it the same thing. By the way my van is a 2000 but made in SEPT of 1999. I bought it in january of 2000.

OK, checked it out, my van has a GU5 not a GU6. Is it the same thing. By the way my van is a 2000 but made in SEPT of 1999. I bought it in january of 2000.

GU5 is a 3.23 ratio.