Packard Forum Index » V-8 (1955-56)

Hello all

Like you maybe know I own 1955 Clipper Custom sedan who is also a export model.I wonder how I could find out what is the rear end ratio on this car.Since this is 1955 I can not have build sheets from Studebaker Museum

There should be a tag on one of the carrier bolts giving the the two numbers of the gear teeth (ring and pinion).
If that is not there, you can place rear axle on jack stands, place car in Neutral, manually turn drive shaft and count revolutions as a wheel makes one complete turn. This should put you close enough to determine which rear-end you have.
Look under group no. 12.001 for available ratios.

Some one please correct me if I'm wrong but if I remember my high school Auto Shop 101 correctly, the preferred method is to eliminate any potential motion of the differential side gears by just jacking one wheel off the ground, counting the drive shaft rotations to rotate the tire 1 full turn, and then dividing by two.

You're quite right Owen, I was just winging it from the top of my head. If I was bald I would have done better.

The clueless here. My speedometer is off by 10 or so miles too low also. So I jacked up one rear wheel, turned it one full turn and counted the drive shaft turns, which were 2. But if I divide by 2, I get 1. That didn't seem right. So I checked my owner's manual and the standard ratio for a 40 1803 is 3.92 or (with Econo-drive 4.36 or optionally 4.09. So I think you would multiply rather than divide in order to get to 4. This is totally based on knowing the correct answer, and not on understanding how it works.

My solution is to take it to a speedometer shop, where for $170 they will check it and install the correct number of teeth so it will read my speed correctly. No longer will I be able to get out of a ticket because of it.

" Yes, Officer, thank you. I will put a 5th wheel on it."

TRy a tachommeter. U'll need to know speed of car in MPH using GPS or mile markers or something and time it. Neeed to know diameter of rear tire wheel assembly. Then do the math to find axle ratio.