Gear ratio ID

[Dave #35697]

67 coupe 327/300 auto
I cannot ID a tag for gear ratio.I found some print on the diff case,thats it!
Any pics.or advice will help.I believe its posi.,both rear wheels turn forward when off ground.
Thanks!

[Joe L.]

Re: Gear ratio ID

Dave-----

For 1967 there is no tag for the differential gear ratio. The differential code is stamped into the bottom of the carrier housing, just forward of where the cover attaches. Often times, the stamping is lightly stamped and difficult to read. You may need to clean it with a wire wheel on a drill or brush and examine it closely with a magnifying glass.

[Dave #35697]

Re: Gear ratio ID

Joe,
Thanks for the quik response!
I can make out the stamping on the diff case,but how do I convert the #'s.
Dave

[Daniel S.]

Re: Gear ratio ID

Dave,
On the bottom of the diff you will find the rear axle assemby code. It identifies the gear ratio, the build date and the plant of manufacture. The first 2 digits of this code indicate the gear ratio.

AK = 3.36 ratio
AL = 3.08 posi
AM = 3.36 posi
AN = 3.55 posi
AO = 3.70 posi
AP = 4.11 posi

Dan

[Dave #35697]

Thanks Guys! Ratio Location! *NM*

[Jack H.]

Caution!

Dave, unless you've owned the car since new, do NOT read the differential case broadcast code and THINK you know the gear ratio inside. OFTEN, prior owners changed pinon/ring in routine maintenance and decided to swap rear end ratio! So, what's stamped on the case may NOT be what's actually inside.

Have a helper rotate the rear wheel through a revolution cycle while you count drive shaft rotations and VERIFY what's actually inside your differential case today....

[Dave #35697]

Re: Caution!

Yes!
I agree,Ring & pinion might have been changed.
How do you check the tire turning method?
Thanks!

[John H.]

Re: Caution!

Dave -

Just jack it up so both rear wheels are off the ground (trans in neutral, park brake off), mark both tires and the prop shaft with tape or chalk, and turn the tire(s) exactly one revolution while you (or a helper) counts the revolutions of the prop shaft. 3-1/2 is 3.55, 3-3/4 is 3.70, four and a tad is 4.11, etc.

[Dave #35697]

Re: Caution! Thanks John! *NM*