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With the great success of the Mitchell overdrive in the Model A’s, I approached Glenn Mitchell in September 2002, asking if he could make a good set of gears for the Model A transmission. At that time the Model A gears being made were dimensioned incorrectly at the inner spline, resulting in poor operation. Since Glenn was in the business of making gears for his overdrive, it seemed like a good idea. After studying the gears required for the Model A transmission, Glenn got back to me some months later and explained that making gears was no problem, but the low quantity needed for the Model A would not make the pricing feasible. But he had a better idea. Put a synchromesh transmission in the original Model A case.
That this time, Glenn and son Steve put their heads together to design gears using their component theory, and to fit everything into a Model A case. Steve spent many hours prototyping gears for this unit. First, they wanted to use the tried and proven syncro assembly that had been so successful in the “Mitchell Overdrive.” Then a cluster gear was designed in several pieces and running over a splined shaft which then enables different ratios to be made. “Henry Ford could not do this because of the one piece forged cluster gear,” Glenn said. But with Glenn and Steve’s theory, ratios can be changed at any time by changing gears in the transmission.
Over the following year, design and fit was experimented with and in late 2003 the first production units were completed and installed in several Model A’s.
The Mitchell synchromesh transmission for the Model A uses the same synchro package (torque lock) as used in the very successful Mitchell overdrive and as used in all T-5 transmissions throughout the auto industry today. The synchro package is the only component in the synchromesh transmission that is a purchased component, other than the sealed bearings. Mitchell Manufacturing makes all of the gears and shaft and gear, the splined output shaft, 2nd gear, low gear, cluster gear and reverse idler gear. The main shaft and idler shaft have the “O” ring cut for an oil seal. The input and output bearings are full sealed bearings. Slight machining modifications are made to the internal Model A transmissions case to allow room for the synchros and gear throw. New shifting forks are machined to fit the new slider gears (second and low) movements.
The clutch (no double clutching) and shift any time, any place and at any speed. Shifting is so smooth it almost shifts itself.
The shifting pattern is a little different than the standard Model A pattern. In that the gearohange between gears is closer.
The Mitchell synchromesh transmission makes driving the Model A an ease with no more foot timing for double clutching or lost torque form double clutching. Just on depress of the clutch pedal at any time at any speed for a smooth shift.
Gear cutter, as well as an accomplished welder and machinist. He also does product R&D and oversees employee production. Cyndi, Steve’s wife, programs and operates the CNC Milling Machines and CNC lathes, does O.D. and I.D. grinding and all assembly of Mitchell products.
Glenn oversees the whole operation, and Sue runs the office, taking orders, scheduling, billing, and customer service. Here is a family operation that produces another quality product for the Model A.
MODEL 1000 OVERDRIVE
The
Mitchell “Model 1000” Overdrive is a totally new, tested and proven 2 speed
synchromesh overdrive transmission. It is small, compact and built “specifically
for Model A Fords.”
Precision built in
America of the
finest alloys and workmanship, assuring you of a quiet, easy shifting and
dependable unit to make your driving a pleasure. For
the “Model A’s” the installation kit includes mew front and rear torque tubes,
drive lines, speedo cable extension and gear, shifter and linkage. Our
overdrive transmission offers many important benefits to older cars that are
geared low. With
RPM reduction of approximately 500-600 (at 55 mph) our 26% overdrive allows a
comfortable highway cruising speed. Not
just an overdrive, with the synchromesh shifting feature, any gear can be split
at any speed, giving you six forward gears instead of three. Shifting is manual
with a separate shift stick, easily floormounted in the cab next to the standard
stick.
Overdrive mounts mid-ship of vehicle and new torque tubes and drive lines are
provided for easy installation. Torque tubes are assembled to overdrive at the
factory.
Speedometer and odometer are read from the overdrive after it is installed,
speedo cable extension and gear are part of the installation kit.
MODEL A FORD RATIOS USING
MITCHELL OVERDRIVE
3.54 26%
OVERDRIVE 2.62
36% OVERDRIVE
2.27
3.78 26%
OVERDRIVE 2.80
36% OVERDRIVE
2.42
4.11 26%
OVERDRIVE 3.04
36% OVERDRIVE
2.63
FACTORS TO FIGURE REAR END
RATIOS
REAR END RATIO X .074 FOR
26% OVER
REAR END RATIO X .064 FOR
36% OVER
RING AND PINION GEAR TEETH
3.54 11 TOOTH PINION
GEAR
39 TOOTH RING GEAR
3.78 9 TOOTH PINION
GEAR
34 TOOTH RING GEAR
4.11 9 TOOTH PINION
GEAR
37 TOOTH RING GEAR
MITCHELL MANUFACTURING
PROUDLY PRESENTS
MITCHELL MODIFIED MODEL A
MAIN TRANSMISSION This
is a totally new main transmission in an original Model A Case. All new gears,
shafts and bearings. New shaft rail, shift forks, spring detents, “O” rings on
Bottom shafts, new bearing sealed both sides on front and rear main shafts.
Synchronised 2nd & 3rd gear for easier shifting and
guaranteed to stay in gear.
ADVANTAGES
Absolutely no alteration to your vehicle. Remove your transmission install the
Mitchell. No additional attachments to purchase. No more grinding gears, no more
double clutching, shifts anywhere, any time and at any speed. Uses the same
gearing technique as used in the Mitchell Overdrive. This option not only
compliments the Mitchell Overdrive but also makes the Model A more easily driven
by any age, male or female, experienced or novice driver, with or without an
overdrive in your vehicle. Use
regular gear oil. |
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