identifying a chevy 4:11 rear end

Quick question. How can i identyfify if the rear end i have in my 58 chevy truck is a 4:11? I also have a 55 chevy rear end and would like to know what gear ratio it is. Can you guys help me out?

 

Easiest way: Chalk mark the pinion, chalk mark the axle end. Spin pinion, count number of revolutions to reach one full turn of axle. 4 turns pinion end to one turn of axle equals 4.11.

 

Non-posi:
Jack one wheel off the ground.
Turn the wheel 2 complete turns.
- Count the turns on the drive shaft.

4.11 turns on the drive shaft equals a rear ratio of 1:4.11


Posi:
Jack both wheels off the ground.
Turn one wheel 1 complete turn.
- Count the turns on the drive shaft.

 

does tire size come into play here ? like if he has really tall tires, will the tire revolution be different than if he has short tires ?
or am i thinking wrong ? you're counting AXLE revolutions correct ?
if so, shouldn't the tires be pulled off to do this?
as dalesnyder said...mark the axle end.

 

Most 55-59 chevy half ton truck rearends were 3.90 ratio.