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 especially if you suspect a previous owner changed out the rear end -
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 tire on the other side of the
driveshaft should be turning at the same rate. Both wheels off the ground is the better
procedure for a limited slip differential.)
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.
If you choose to lift just one of the rear wheels off the ground, change the above
procedure by rotating the tire TWO full turns. (With one wheel on the ground and not
spinning, the ring gear turns half as much. 2 turns of the lifted wheel = 1 turn of the ring
gear.)
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