What Is This Part?

[metaldad]

Going thru the extra parts acquired thru the purchase and ownership of a 68 coronet 500 convertible.
i will be putting up parts for sale.
this doodad was in a box of random parts.
any idea wth this is?

 

[rmchrgr]

Speedometer gear. Goes in the transmission tail housing and meshes with the output shaft to determine your road speed.

Count the number of teeth on it to determine the it's ratio that would match it to a rear gear - 41= 4.10 gear, 39 = 3.91 and so on.

 

[Cranky]

And when you install one you have to make sure it's 'clocked' in the right position for it to work right. If it's clocked too far one way, it will get eaten up and too far the other way, it won't work at all. The adapter is marked for the corresponding ratio number. Also, if you run oversized tires, it will change the speedometer reading and there are charts to help pick the right speedometer pinion gear to insert to correct the reading. Next!?

 

[metaldad]

thanks guys. it's in the boxes of parts received from p.o., who restored/built the car.
original rear was a 2.76. i assume zero market for it.
car has now 3.91

 

[Beekeeper]

What is the tooth count 40? Tooth count is molded into the gear

 

[66Satellite47]

The tooth count is usually molded inti the gear. It doesn't necessarily relate to the ring & pinion ratio. The current tire sizes do not really relate to the sizes shown in a service manual. Several charts for speedo pinion and modern tire sizes are on the net. A speedo pinion for a 2.76 gear may not be high demand, but who knows. Thats why I keep all from my 727 collecting days.

 

[hunt2elk]

The number of teeth do not correspond directly to the rear gearing like stated above. 41 does NOT mean it necessarily goes with a 4.10 gear set. Rear tire diameter is the other key part to that equation.