Chevrolet Suburban Forum : “Axle Ratios?”

There is a way to get a rough estimate.
On a lift mark the top of the tire with chalk
Mark the differential to drive shaft with chalk
Rotate the drive shaft as many times as it takes to get the tire to rotate one turn. If it turns a little over 4 times its 4;10-4.11
under 4 turns you would have to figure out 1/2 3/4 turn etc and see what ratios they had in that year and figure which is closest
TO do it exactly pull the cover and on the ring gear will be marked teeth for pinion and ring gear / divide the ring number by the pinion number ( teeth )

Just check the tag off of one of the diff cover bolts, little metal tab will tell you gear ratio if it's still there, I would bet money they are 3.73's though.