Differential gear ratio

[Paul L.]

I cannot seem to find the gear ratio for the installed unit on my 1966 coupe.
It is a positraction unit but other than that, I cannot determine the ratio.
I am almost sure it is not of the 4.11:1 variety but I am not sure.
Please give me some information as to where to look for the codes for this.

Thanks,
Paul

[Michael M.]

Re: Differential gear ratio

Paul, you should have a differential casting number which is located on the rear of the cover upside down (#3871375). The casting date is located below the drivers side output flange. The assemblly date is stamped on the bottom of the case with the axle code.

[Ronald L.]

Re: Differential gear ratio

Jack up the car and spin one rear tire by hand.

If both wheels go the same direction you know you have a posi.

Then you need to mark the drive shaft and cound the tire revolutions per one turn of the drive shaft.

For a 4.11, it will be a little more than 4 turns.