Specifications

How do I determine my rear axle ratio?
The actual ratio should be stamped into the axle housing. It will usually be found on the
forward portion of the axle tube on the right side. Probably pretty gummed up and difficult to
read too.
The stamping on the housing is read as follows:
First 3 digits indicate the rear axle ratio. (you can stop right here)
Next digit indicates the build source C=Buffalo, K=Canada
Next 3 digits indicates the day built - expressed in Julian Date form
Last digit indicates the shift 1=1st shift, 2=2nd shift. (Don't have any idea what the purpose
of this is.)
Another way is to try and find the RPO codes sticker somewhere in the coach, your Chevy
dealer can interpret it for you. The RPO info I have is:
RPO 066 is 4.10
RPO 005 is 4.56
Don't have info for the 4.88 or any others.
Those are the easy ways.
The hard way is a little more difficult with a motorhome than with a car, but is absolutely the
most accurate - here goes:
Raise the rear axle off the ground, support, support, chock front wheels and then support
some more to make sure it is safe. Transmission should be in neutral and emergency brake
off (chocks - remember?). You are going to be UNDER this thing.
Make a BIG chalk mark on one side of the driveshaft that can be seen from alongside the
vehicle (you don't really want to be under it very long for this). Make a corresponding mark
on the side of the housing that aligns with the driveshaft mark, on the pinion housing would
be good.
Now make a mark on the right rear tire either exactly at the top or exactly at the bottom.
Maybe make a corresponding chalk mark on the fender for alignment purposes. The
objective is to SLOWLY rotate that tire one complete revolution while someone watches the
drive shaft chalk marks and counts the revolutions.
The number of turns the driveshaft makes indicates the ratio. In other words, 4 complete
revolutions and almost another full one is probably a 4.88.
http://users.sisna.com/cebula/P-Chassis-AlignmentProcess.pdf 30 Version 0.7 –Sep 14, 2005