Model A

Ford Garage

Model AA Four Speed Transmission

in a Model A Chassis

In 1931 Ford offered a factory option to install the Model AA Ford truck four speed transmission in a Model A chassis on special order.

This offering was documented in the July 8, 1931 Indianapolis Branch Dealer Service Letter above, as well as the 1950 edition of the Ford "green bible" Chassis Parts Book, as used by dealership service parts departments.

Typically the four speed trans is found on pickup trucks, though the 1931 Branch Service Letters do not indicate any restriction on which models Ford would install it in. It is possible other people such as rural route mailmen ordered it in coupes and tudors.

Pictured above is the Ford drawing for the A-7092-D universal joint front knuckle, which was released in 1931 as part of the A-7090-C universal joint assembly for special equipment use (see note in lower left). This unique universal joint was to enable the mounting of the 4 speed Model AA truck transmission in a Model A chassis.

This knuckle is similar but different to the 81C-7090 universal joint used on the 1938 Ford pickup with four speed truck transmission. (That 1938 transmission was essentially the same as the AA transmission, except for some case details).

It is possible to modify the front knuckle from an 81C-7090 universal joint to work with the Model AA transmission in a Model A chassis. NOS 81C-7090 universal joints are 'relatively' easy to find.

The A-7090-C universal joint assembly has the special and unique A-7092-D (AA 10-spline) knuckle on the front and the typical Model A 6-spline drive shaft knuckle on the rear.
Pictured above is the Ford drawing for the A-7085-E transmission rear bearing retainer which was released in 1931 for special equipment use on the 4 speed Model AA transmission when mounted in a Model A chassis.

Though the correct A-7085-E retainer appears similar to the typical AA-7085-B retainer shown below, it is actually smaller. (one inch total thickness)

The A-7085-E retainer is the proper retainer for use in the Model A chassis. (also note the A prefix part number on the drawing, not AA). The AA- prefix retainer is for use in an AA chassis.
Pictured above is one side of the typical AA-7085-B rear bearing retainer used in 1931 in the Model AA Ford truck chassis. This retainer has an overall total thickness of 1.375 inch and is too thick for use in the Model A chassis. Pictured above is the opposite side of the AA-7085-B retainer as used in a Model AA truck chassis. Note the AA-7085-B part number cast-in.

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 AA Four Speed Transmission Case Cracks
  3. 1929 to 1931 Model AA Four-Speed Transmission Clutch Housing
  4. Model AA Warford Sextette Sub Transmission
  5. Model AA US Army 1931 Model AA 157" WB Trouble Truck
  6. Model A & AA US Army 17th Field Artillery Ford Motorized Battery
  7. Model A Flywheel Housing Cracks
  8. 1928 to 1934 Double Sealed Transmission Ball Bearings
  9. Model A Ruckstell Dual High Transmission
  10. Model A Mitchell Synchronized Transmission
  11. Model A & B F-150 TOD Transmission Conversion ~ Tremec T170FT RTS

January 2004