Originally Posted by Rider
This is what I've found by vin -
REAR Axle Ratio (:1) - Rear 4.10, 4.56, 3.73 3.73 min 4.56 max
I believe that the rear axle ratios you've quoted are all that were installed in these buses, but that list does not include any of the posi-traction or locked rear options that were used.
Of the three ratio's, 3.73 would be your best bet for cruising speed and fuel economy.
I've read that if you take the VIN number to a GMC dealership parts department, they can get a build out sheet which will tell you the rear axle that was installed in your bus.
If you decide to do this I would suggest that you go to the dealership yourself and do not call!!! Most dealerships will not do this over the phone. Also, do not go at or near lunch time or closing time.