Transmission Speedometer Gear

[Gerald C.]

Re: Transmission Speedometer Gear

Joe,

Thanks for the follow-up information. I bought the car a couple of years back and never drove it. Just disassembled it for a full body off restoration. So I can really answer your question as to what the driven gear that was in the car. Currently, the speedometer is very accurate because I've driven through a few speed warning signs going into downtowns and school districts. In addition, I had a follow car behind me verifying the accuracy. The tires on the car are the correct bias-ply 6:70:15.

Thanks again!

Jerry

[Joseph L.]

Re: Transmission Speedometer Gear

Hi Jerry
Maybe diameter sizes will help with understanding your issue.

As Joe said above, you had a red 21T driven gear that did not work. If you measure the diameter of the gear, a new one is 0.81". It is designed to be used with only a 1.84" diameter drive gear.
You installed a green 22T driven gear. A new green 22T gear has a diameter of 0.87". This gear (that works for you) is designed to be used with a 1.74" diameter drive gear.

From this information, the drive gear in your transmission is 1.74" diameter. You cannot use the smaller diameter driven gears in the current transmission configuration. The gears do not mesh (teeth do not touch).

green 22T driven gear (0.87" diameter)---- 1.74" diameter drive gear
red 21 T driven gear (0.81" diameter)---- 1.84" diameter drive gear

Also, if you try the other way (0.87" driven, 1.84" drive), the plastic driven gear will be destroyed after a short while.

Joe

[Gerald C.]

Re: Transmission Speedometer Gear

Joe,

Thanks for the update. Much appreciated.

Jerry