Very useful posting, thank you for documenting what you've done and including pictures. This will come in handy later. Do you know if the axle in your truck is stock? I'm assuming the truck is a '56 Chevy 3200. I've been trying to determine if the rear end in my 55 1st was original and your pictures look identical to what's in my truck. From this forum I've learned that at least the 55 1st & 2nd used the same axle. My engine & tranny was swapped by a previous owner, a 350 & 400 Hydra from a '72 Camaro. I determined the gear ratio to be a 3.90 by turning the driveshaft just short of 2 rotations to turn the rear driver's side wheel once.
Someone else had posted the following on this forum.
"Can I put math in a sentence? (number of drive shaft revolutions) divided by (number of tire revolutions) times 2 would give the approximate gear ratio. If you have 4.11 gears expect to see the drive shaft turn just more than twice for each turn of the wheel.
If your gears are 3.90 you'll see just less than two turns of the drive shaft for each turn of the wheel"
