To Entire DURANT Organization:
The following information will undoubtedly be of value to you in the installation of steel flywheel ring gears now being used on all Models, the adoption of which part was announced to you in Service Bulletin S-32.
The inside dimension of Flywheel Ring Gear - Part No. 26765 used on the Models M, M-2, M-4, 40, R, 55, 60, 70, 75, S-4 and 401, is 12.982". The inside dimension of Flywheel Ring Gear Part No. 26850 - used on models 63,65 and 66, is 12.373".
When installing either one of these ring gears on flywheels used prior to the adoption of these steel ring gears, the flywheel should be machined so that the outside dimension is .020 larger than the inside dimension of the ring gear being installed. This will permit a shrink fit of from .017 to .020 when permissible tolerance of .004" in the inside dimension of the ring gear is taken into consideration.
The proper heat for the shrink fit of the ring gear is from 560 degrees to 570 degrees Fahrenheit and the ring gear should be quenched with water immediately after being placed on the flywheel. In all cases the tooth chamfer should be on the side of the flywheel next to the motor.
Yours very truly,
Director of Service
M to O incl. S-89