Model A

Ford Garage

Mitchell Synchronized Transmission

Shown below are pictures of the Model A transmission which is rebuilt by Mitchell Manufacturing using all new internal gears and 2nd and 3rd gear synchronizers. This transmission comes with a 15% higher 2nd gear.

Be cautious of increasing only the 2nd gear ratio to 15%. It is questionable if it is worth the cost just for the synchros and improved 2nd gear, without also getting the improved 1st gear ratio.

A 15% higher 1st gear ratio is also available, together with the 15% higher 2nd gear. The resulting transmission has many desirable similarities to the 1932 Model B transmission, without having to install a Model B engine and transmission in a Model A, together with the necessary wishbone and pedal mounting.

The resulting combined 15% higher 1st and 2nd gear transmission improves general drivability especially on flat ground or with a higher output torque engine.

Shown above is the view of the reworked shift tower with the new forks and shafts as assembled by Mitchell.

These transmissions are quite expensive and are not an overdrive, but the revised and improved gear ratios and synchronizers make the car much more drivable than the stock Ford first and second gear ratios.

Contact: Mitchell Manufacturing

Mitchell Manufacturing
1157 Parker Street
Colusa, California 95932
(530) 458-4500
(800) 859-2088 Toll Free
Mitchell Manufacturing web site.

Drivability and Suitability ~ Recommended Combinations

Blue-shaded attributes are equivalent to the stock Model A.
Green-shaded transmissions, ratios, and attributes are preferred for improved drivability compared to stock Model A.
Yellow-shaded attributes are questionable, and Red-shaded are the least desirable.
Three Speed
Transmission		 Rev 1st 2nd 3rd 4th % OD Optimal Drivability and Suitability ~
Recommended Combinations and Usage Notes

Stock Model A
1928-31		 3.745:1 3.12:1 1.85:1 1:1 ~ ~
  • 4.11 rear axle in a heavy-medium weight car and/or hill terrain.
  • 3.78 rear axle in a medium-light weight car.
  • 3.54 rear axle in a light weight car and/or flat terrain.

Stock Model B
1932-34		 3.383:1 2.820:1 1.604:1 1:1 ~ ~
  • 4.11 rear axle in a heavy-medium weight car and/or hill terrain.
  • 3.78 rear axle in a medium-light weight car.
Synchronized 2nd and 3rd gears.
Taller 1st and 2nd gear ratios compared to Model A.
When coupled with a 27% Laycock, or 26% Mitchell driveshaft overdrive unit (or 36% OD unit with a 4.11:1 axle), this transmission would be an excellent solution for both low speed and high speed drivability, though without an internal transmission overdrive gear.
CON: Significant added Mitchell OD mass on torque tube.
CON: Extra OD shift lever on floorboard with Mitchell OD.

Mitchell Synchro
15% 2nd only
Model A		 3:12:1 1.61:1 1:1 ~ ~
  • 4.11 rear axle in a heavy-medium weight car and/or hill terrain.
  • 3.78 rear axle in a medium-light weight car.
Synchronized 2nd and 3rd gears.
15% Taller 2nd gear ratio is similar to Model B.
CON: Expense of Mitchell transmission, but no improvement in 1st gear ratio.

Mitchell Synchro
15% 1st & 2nd
Model A

plus

Mitchell
26% TT OD		 2.71:1 1.61:1 1:1 ~ 0.79:1

26%
  • 4.11 rear axle in a heavy-medium weight car and/or hill terrain.
  • 3.78 rear axle in a medium-light weight car.
Synchronized 2nd and 3rd gears.
15% Taller 1st and 2nd gear ratios are similar to Model B.
When coupled with a 26% Mitchell torque tube overdrive unit (or 36% Mitchell OD unit with a 4.11:1 axle), this Mitchell transmission approaches the "Goldilocks" 3+1 OD RTS transmission solution for both low speed and high speed drivability, though without an internal transmission overdrive gear.
CON: Significant added Mitchell OD mass on torque tube.
CON: Extra OD shift lever on floorboard with Mitchell OD.

Mitchell Synchro
15% 1st & 2nd

plus

Laycock J-Type
27% TT OD


My 1930 Coupe
w/ 3.78:1		 2.71:1 1.61:1 1:1 ~ 0.79:1

27%
  • 4.11 rear axle in a heavy-medium weight car and/or hill terrain.
  • 3.78 rear axle in a medium-light weight car.
Synchronized 2nd and 3rd gears.
15% Taller 1st and 2nd gear ratios are similar to Model B.
The 27% Laycock J-Type electro hydraulic planetary torque tube overdrive, combined with this Mitchell transmission, exceeds the "Goldilocks" 3+1 OD RTS transmission solution for both low speed and high speed drivability, but without an internal transmission overdrive gear.

PRO: Lightest weight torque tube OD, and with benefit of an electric shift switch.
PRO: One-for-one transmission, torque tube, and drive shaft swap. No other driveline modifications. No levers, no cutting or modifying radius rods, torque tubes, crossmembers, brakes, etc.


Words of Warning About Lubricants

API GL-4 versus GL-5 Specification:
Owners should be aware that there is a disconnect between what oil Mitchell recommends for this gearbox versus what established engineering, history, and the American Petroleum Institute (API) would otherwise dictate.

Mitchell recommends using "One quart of any good grade of 85-140 weight gear oil, either synthetic or petroleum-based, with a GL-5 rating"

However, The Mitchell transmission contains brass blocker rings in the synchronizers, as did many older vintage manual transmissions (which cannot tolerate current API GL-5 oils).

GL-5 should never be used if brass or bronze is in the gearbox.
The sulphur/phosphorus in GL-5 lubricants is corrosive to brass in the synchronizer.

GL-5 was originally developed for extreme pressure applications like hypoid rear axle ring and pinion sets.
Model A spur gears do not need or benefit from GL-5 spec, and GL-5 is specifically not recommended by the API for gearboxes containing brass or bronze.
GL-4 lubricants should be used in the Mitchell transmission, IMO.
Mitchell may have chosen the GL-5 not knowing the gear oil history, or believing that "newer is better" for lubricants, or simply because GL-5 is readily available today at every auto parts store.

GL-4 may be somewhat more difficult to find since most modern manual transmissions, transfer cases, and rear axles no longer contain brass components, and thus the industry has largely moved on from the older spec GL-4 to the typical current GL-5 spec lubricants.

Suitable available lubricants to consider:
Valvoline High Performance 85W-140 Conventional Gear Oil GL-4
CRC SL24228 Sta-Lube SAE 140 Gear Oil GL-4
Driven STF Synchromesh Transmission Fluid (75W-85 GL-4)

More related information on Ford Garage:

  1. For more Model A & B related information, use the Site Search box at the top or bottom of this page.
  2. Model A 1928 Gear Shift Lever and Tower Assembly
  3. Model A Transmission Shift Lever Differences
  4. Model B Transmission Shift Lever
  5. Model A Shift Lever Butler Finish Details
  6. Model A Shift Lever Spring Compressor and Removal Tool
  7. Model A Ruckstell Dual High Transmission
  8. Model A & B Gear Shift Lever Ball Variations
  9. Model A & B 1932 Los Angeles Olympics Shift Lever Ball
  10. Model A & B Rear Axle Gear Ratios
  11. Model A & B F-150 TOD Transmission Conversion ~ Tremec T170FT RTS

March 2003