Introduction


The Mustang pictured below (bottom) was first purchased by my father-in-law, Buddy, in 1986, in Connecticut. Shortly after, he purchased a second six-cylinder convertible and sold the pictured one to my wife's cousin, Ronnie. Dad died in 1994. When Ronnie decided to sell the car to finance an in-ground swimming pool in 2006, my wife Sharon and I decided to buy it, and brought it home to Tennessee.
The car had undergone a cosmetic restoration before Dad bought it, and apart from some minor detailing since then, was still in the same condition when we bought it.
In June 2010, I found out it was a Sprint 200, Package A, 3-speed manual transmission. And after reading an article in the archives of the Mustang Times by Jim Smart, went looking for the Broadcast (Build) Sheet. I found it wrapped around the wiring harness behind the speedometer. After a brief search to find out what all the codes meant, I realized that surprisingly little is known or published about these documents. So I decided I'd try to attempt to decode it myself. This blog is a journal of that research.
All discussions below currently pertain to only 1966 Mustangs.

Wednesday, October 6, 2010

Speed-O-Gear

On the Broadcast Sheet:
The 8th box from the right on the bottom row has a code for the Speed-O-Gear.
The National Parts Depot (NPD) catalog has a formula for selecting the appropriate gear - their part #17271.
I also did some research and found that the tire diameter for the original  6.95 x 14 tires, that came on all early Mustangs, was 25.3".
This data should yield the solutions found in the following table - to which I'm beginning to tabulate codes for the particular gear combination.

Popular modern tire sizes can only approximate the original 6.95 x 14 tires (797.1587 tire revolutions per mile). Speedometer accuracy may suffer as a consequence. P195/75R14 tires are about 3/4" wider than the original tires and turn 790.4183 revolutions per mile. P205/70R14 tires are about 1" wider and turn 797.1835 revolutions per mile (probably the closest modern tire diameter). Please see the following Mustang Monthly article for a detailed discussion:
http://www.mustangmonthly.com/techarticles/mump_0511_best_ford_mustang_tires/sizing.html



Drive Gear = 7 for < 3.50 and 6 ≥ 3.50
6.95 x 14 Tire Size = 25.3” Diameter = 797.1587 Tire Revolutions per Mile
(7 or 6) x (Axle) x (797.1587) / (1000) = Drive Solution
Axle
Drive
Solution
2.77, 3.03, C-4 Type 1
C-4 Type 2, Dagenham
4-Speed Borg Warner T-10
4-Speed Ford Toploader
3.20
17.86
B
RH 18 – Yellow
-
Not Available
2.83
15.79
A
RH 16 -
-
Not Available
2.80
15.62
B

A
3-Speed
RH 16 -
C-4

-

LH 16 – Brown/Orange
3.00
16.74
K
RH 17 – Green/White
G
LH 17 – Purple
3.50
16.74
-
RH 17 – Green/White
G
LH 17 – Purple
3.89
18.61
-
RH 19 – All Pink
-
LH 19 – Pink End
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