Speedometer gear to adapt to rear end change

[67D100Pickup]

I have a 1967 D100 318 3 speed. I switched out the rear end from a 355 to a 272 and need to swap the speedometer gear to accommodate this change.

I think it has an A745 tranny but you can see my discussion about that here...

viewtopic.php?f=19&t=43386

Can I swap the gear? Do you know what size I need and where to get it?

Jeff, not a mechanic

[martincom]

The transmission type will not make a difference.

In addition to rear axle ratio, you'll need to know tire size. The factory service manual will have a chart which will indicate the number of teeth required, for the speedometer pinion, for a given rear axle ratio and tire size. There are also a number of online charts. Search for Mopar speedometer pinion chart or Chrysler speedometer pinion chart.

The housing the speedometer pinion is inserted to will have tooth number range marks. Be sure to align the appropriate range index mark with the index mark on the tail shaft housing.

Also, lift the vehicle from the rear only when changing. This causes the fluid to pool at the front of the transmission and you will not get a bath of it when removing the speedometer pinion housing.

Ebay and a number of online suppliers offer speedometer pinions.

[sixpak340]

Do these older truck transmissions use the same speedometer pinions as cars of the same era?

If so, some list the tooth count on the gear while newer versions list the last two digits of the part number.

[martincom]

Do these older truck transmissions use the same speedometer pinions as cars of the same era?

I would speculate it depends on your definition of "old" and the size of the truck.

If so, some list the tooth count on the gear while newer versions list the last two digits of the part number.

I haven't seen that before. All I've encountered have the tooth count molded into them. I wonder if the other is a repop?

[sixpak340]

Not a reproduction, same part from a newer OE application.