Rear end ratio

I have an old torque tube rear end out of a 50's era chevy. It's the closed driveline and it's not on anything so I can't just turn the wheels over to find the gear ratio. I pulled the back off of it and the ring gear had 39 11 stamped on it though. 11 / 39 = 3.55 is that the rear end ratio?

 

With the rear cover off you should be able to count the teeth. If they match the stamped numbers, question answered.

 

Yes, 11/39 would be 3:55. It would be from a 50-54 powerglide car.

 

and the brakes should tell you if it's 50 or 51 up, the 51-54 used modern self energizing brakes, 50 had the old Hucks.

 

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

3.55 turns on the drive shaft equals a rear ratio of 1:3.55

Be accurate when counting:
49-52 stick ... 4.11
53 stick ... 3.70
50-54 PG ... 3.55



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