REMOVAL & INSTALLATION
The speedometer cable connects a rotating gear within the transmission to the dashboard speedometer/odometer assembly on 1983-95 Pick-ups and 1983-93 Monteros (1994-95 Monteros use an electronic vehicle speed sensor). The dashboard unit interprets the number of turns the made by the cable and displays the information as miles per hour and total mileage.
Assuming that the transmission contains the correct gear for the car, the accuracy of the speedometer depends primarily on tire condition and tire diameter. Badly worn tires (too small in diameter) or overinflation (too large in diameter) can affect the speedometer reading. Replacement tires of the incorrect overall diameter (such as oversize snow tires) can also affect the readings.
Generally, manufacturers state that speedometer/odometer error of up to 10% is considered normal due to wear and other variables. Stated another way, if you drove the vehicle over a measured 1 mile (1.6 km) course and the odometer showed anything between 0.9 and 1.1 miles (1.45 and 1.77 km), the error is considered normal. If you plan to do any checking, always use a measured course such as mileposts on an interstate highway or turnpike. Never use another vehicle for comparison; the other vehicle's inherent error may further cloud your readings.
The speedometer cable can become dry or develop a kink within its case. As it turns, the ticking or light knocking noise it makes can easily lead an owner to chase engine related problems in error. If such a noise is heard, carefully watch the speedometer needle during the speed range in which the noise is heard. Generally, the needle will jump or deflect each time the cable binds. The needle motion may be very small and hard to notice; a helper in the back seat should look over the driver's shoulder at the speedometer while the driver concentrates on driving.
The slightest bind in the speedometer cable can cause unpredictable behavior in the cruise control system. If the cruise control exhibits intermittent surging or loss of set speed symptoms, check the speedometer cable first.
Some cables do not attach directly to the speedometer assembly but rather to an electrical pulse generator. These pulses may be used for the meter and mileage signal. Additionally, the electric signals representing the speed of the vehicle can be used by the fuel injection control unit, the cruise control unit and other components. To change the cable:
- Unscrew the outer collar where the speedometer cable enters the transmission, and disconnect the inner cable.
- Follow the appropriate procedure and remove the instrument cluster from the dashboard. On most models, the cable housing can be released from the back of the instrument cluster with a simple release tang. On some models, pull the cable toward you (out of the dash) and then release the lock by turning the adaptor to either the left or right. Remove the adaptor.
- The inner cable may now be pulled out of the cable housing from inside the car.
- Install the new cable into the sheath. It's a good idea to check the sheath for binding or kinking. The routing should not contain any sharp bends or angles. A little lithium grease brushed onto the inner cable before installation can be very helpful. Keep the grease at least 1 in. (25mm) away from the speedometer end to prevent messy accidents.
- The cable is square at either end in order for it to engage the speedometer and transmission fittings. Engage the inner cable by rotating it as you insert it. You'll be able to feel when it fits into its slot. Connect the outer cable at the instrument cluster.
- On the transmission end, screw the outer cable connector securely onto the transmission housing. Make certain the cable is secure.