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My 29 AA (early November) has a speedo drive gear marked 6.6-1 with 17 teeth. It has a oval speedometer and a bevel
gear rear axle. I think it is high speed. Is this drive gear correct ?

The high speed gear is marked 5.14
I think the picture is Neal's.
Bob

If you want to find out if your rear end gears are high speed jack up one rear wheel, put truck into third gear, rotate engine with crank one full turn. If the wheel off the ground turns just a hair over three revolutions it is a high speed. Any more than that it is low speed.

Crosscut. It is a lot easier to read the ratio from the speedo drive gear.

Chris Haynes wrote:Crosscut. It is a lot easier to read the ratio from the speedo drive gear.

True... but the speedo gears may not always be correct and others might benefit from a different way of checking a rear end.

Dave, don't you mean High Gear, which may be either third or fourth.

ModelAkid wrote:Dave, don't you mean High Gear, which may be either third or fourth.

I was assuming that the original post was refering to a worm drive rear end. Third gear was the high gear in those trucks.
I don't think that this method works with the 30/31 trucks with bevel rear end and 4 speed transmission.

AA four speed transmissions came out around mid-1929.

My 8-30-29 has 3 speed transmission with worm gear rear end. with high speed rear end with the low speed gear in the torque tube.

Correcting myself: The Judging Standards say the AA 4-speed transmission began in October '29, not mid-29. I had a June '29 AA with a 4-speed tranny but someone must have changed it, probably when the 1930 engine was installed in it.

if the 4th gear in the 4 speed is a 1:1 ratio it will be the same as the 3 speed's 3rd which is a 1:1 ratio.