You’ve got questions, we’ve got answers. We work with the Summit Racing tech department to help you tackle your auto-related conundrums. In this week’s Mailbag, we’re discussing mating an electric speedometer to a cable-driven Turbo 350 transmission.

1954 Chevrolet 3100 Pickup
(Image/Summit Racing)

Q: I have a Chevy pickup truck with a 350 engine, a Turbo 350 transmission, a 9-inch ford rear axle with 3.50 gear, a limited-slip differential, and Mickey Thompson 31-18.5 rear tires.

My problem is with the speedometer. It works with an electric sender and I have the old style Turbo 350 that uses a cable-driven speedometer. How can I get the electric speedo to work with the transmission?

A: There are aftermarket electric speedometer sending units that screw into the transmission where the cable would normally go. VDO makes a good one. You might need to change the speedometer gear for the transmission to correct the speedometer reading. You should be able to get that gear at a local GM dealer.

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