Finding out gear ratio in 12 bolt
 

Hey all - looking for some help and info. I recently bought a 61 pig-nose c10. the 10 bolt rear is bad and I found and purchased a 12 bolt from a 63 C10 ( at least I'm told ). Anyway i would love to confirm what ration it has. The stamping on the axle is as follows:

Ha 01 15

Thanks for the help.

https://67-72chevytrucks.com/vboard/...1&d=1760850322

Re: Finding out gear ratio in 12 bolt
 

Turn the pinion and see how many times it takes to turn the wheel one full revolution

Re: Finding out gear ratio in 12 bolt
 

Pull the cover and count teeth. Change the fluid while you are at it.

No telling what's in there after 60+ years.

K

Re: Finding out gear ratio in 12 bolt
 

I was unable to find the HA code.

The gear ratio codes are located on the front passenger side of the differential as shown in the illustration below. This code will tell you the ratio, whether it is posi or not, any special notes and what plant it was made at.

Re: Finding out gear ratio in 12 bolt
 

so here are the stamped numbers on the axle:
Ha 01 15 w

Here are the numbers on the ring gear inside the 12 bolt:
3817778 11:41 gm 12-67 1

here are the numbers on the outside of the carrier near the yoke:
N 3896838

Re: Finding out gear ratio in 12 bolt
 

The 11;41 means 3.73 gear.

Re: Finding out gear ratio in 12 bolt
 

Is the stamp “HA” or “Ha”?
Found this on another site, could it be a 1965 12 bolt? If so it does look like it’s a 3.73/ non Posi

Re: Finding out gear ratio in 12 bolt
 

HA.

Broadcast (pick) codes are always all upper case.

K

Re: Finding out gear ratio in 12 bolt
 

Correct. (41 ring gear teeth divided by 11 pinion gear teeth) = 3.727273 which rounds to 3.73