How to Fix the Speedometer Cable on a 1989 Ford Mustang

If the speedometer cable no longer functions as it should, the mechanical portion of the speedometer cable, the pinion gear and seal, has probably failed. The gear and seal acts as a transfer point between the throttle body and speedometer cable. Without it, the speedometer cable can't relay the engine speed back to the car's instrument cluster. However, most novice mechanics can change this gear and seal in a few minutes, acquiring a correctly-operating speedometer.

Tools Used: Socket set, Small standard screwdriver

Fix the Speedometer Cable

Loosen the bolt on the speedometer cable retaining bracket with a socket wrench. Pull the bracket and bolt off of the throttle body. Follow the long air intake tube which attached to the throttle body. The bracket is attached to the throttle body, is L-shaped, and has an attached speedometer cable and small housing at the end of the speedometer cable.

Pull the pinion gear assembly straight out of the housing.

Remove the retaining clip from the pinion gear with a small standard screwdriver, then slide the gear off of the speedometer cable.

Remove the O-ring from the pinion shaft with a small standard screwdriver.

Lubricate the new O-ring with engine grease. Push it into the pinion shaft retaining groove with a small screwdriver.

Push the replacement pinion gear into the shaft and engage the retaining clip with a small standard screwdriver.

Place the pinion gear assembly and bracket onto the throttle body, sliding it over the speedometer cable. Install the speedometer cable bracket retaining bolt with a socket wrench.

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