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Upgrade The Gauges In Your 1967-1972 GM Truck With Classic Instruments

Author: Todd Ryden | 01/12/2022 < Back to Motor Life Home
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Some may say that the instrument cluster of the 1967-1972 GM C10 pickup was nearly perfect in terms of ergonomics and function. A large, easy-to-view speedometer and fuel gauge across a flat plane along with supporting gauges across the bottom (when included). The rare tach option right in the middle of the dash is icing on the cake and was great placement for tow rigs and work trucks.


Classic Instruments thoughtfully reviewed the second-generation C10 dash design and didn’t set out to reinvent the overall concept and feel of the original dash. Rather, they embraced the layout to simply refine the placement of the gauges, the accuracy, and overall appearance. Their solution is a completely wired set of modern electronic gauges featuring a 4-5/8-inch speedometer and tach separated by a 3-3/8-inch clock that’s then complemented with a quartet of 2-1/8-inch fuel, oil pressure, coolant temp, and voltage gauges. Fresh turn signals and a bright light indicator are also in place.


To make installation simple, the gauges area is mounted securely into an all-new dash panel with the wiring all tied together into one 15-pin connector. This makes installation basically a direct bolt-in once you splice the OEM wiring into the supplied mating connector. In our installation, we used the factory turn signal wires, high beam indicator, temp sensor, dash lights, fuel level, and power wires. That left only routing new wires for the tach, clock, oil pressure, ground, and the speedometer wiring.


Speaking of the speedometer, Classic Instruments has nearly any application covered, thanks to their built-in Zeus Speedometer Technology (ZST). This advanced system will connect to a pulse signal generator, Vehicle Speed Sensor signal, or an output from an ECU, which is used in many late-model drivetrain swaps. This makes for an easy installation with no external boxes or accessories to wire.


The 1971 Chevrolet C10 we used for this installation has a 700-R4 transmission with a mechanical speedometer, so Classic Instruments supplied a pulse generator sensor that screws right in place of the cable on the trans and connects to the dash with a three-wire harness. New sensors for oil pressure and coolant temp are also supplied, which made for a complete package, requiring no extra parts or trips to the speed shop down the street.


Like the ZST speedometer, the tach can also be programmed for use with a standard distributor-triggered ignition or for a coil-per-cylinder system, such as an LS-series engine. The default is for a distributor, so we didn’t have to set up the tach, but this is a simple procedure similar to calibrating the speedometer or even the clock. Classic Instruments includes momentary switches that are connected between the ground and gauge that allow you to enter the calibration mode without the need for any complicated tools.


One unique option Classic Instruments recently introduced is a digital information display on the speedo. This display features a unique rolling odometer that, at casual glance, appears stock but with the click of a button it switches to a numerical speed display or a trip odometer (and a choice between miles per hour and kilometers per hour). The display is also used when calibrating the speedometer and even troubleshooting.


Our 1971 is largely original from the inside out, so we opted for the G-Stock series of gauges due to their factory styling with modern looks. Classic Instruments offers most of their different series of gauges in the C10 package or you can opt for a completely custom gauge set to match the theme of your build. The installation of the gauge set was as straight forward as it gets. Installing new terminals on the factory wiring requires patience and skill, like any wiring project, and is made much easier when using a professional crimp tool. However, with no additional boxes to mount, the wiring was a snap.


Calibration of the speedometer was a breeze and the digital odometer continues to mesmerize us as we roll down the road. For the first time, our Suburban has a full brace of accurate, functioning gauges combined with a modern look in a classic package.

Classic Industries C10 Cluster Removal 1

The nice thing about removing the dash on a 1967-1972 model is all it takes is six screws, the speedo cable, and the oil pressure line (if equipped). Still be prepared for a light yoga body bend to get behind the dash.


Classic Industries C10 sensors

Electronic sensors for the coolant temperature and oil pressure are also supplied. Note the black momentary switch; these are used to calibrate the tach, speedo, and to set the clock.


Classic Industries C10 Cluster New Terminals

With the sensors in place, we moved onto the wiring. New terminals were supplied along with a 15-pin connector. The barrel-shaped terminals have two sets of crimp tabs, one for the sleeve of the wire and one set for the copper strands. This crimp procedure is much easier with the right tool (we used crimp dies for Weather Pack terminals).


Classic Industries C10 Cluster Socket Wiring

At this point we were over the halfway point in our wiring. The remaining sockets were filled with three wires from the speed generator, a tach signal from coil negative, and a full-time 12V source for the new clock.


Classic Industries C10 Cluster gauge wiring bundle

Classic Instruments handles all of the wiring so all you need to do is plug in the one connector. The gauges are mounted firmly in an aluminum plate.


Classic Industries C10 Cluster Speedometer Application Switch

Before installing the dash, there is one switch to confirm that the speedometer is set up for your application. The switch needs to be in the “on” position for an ECM or SN16 signal, or turned to “off” for a VSS or SN96 signal.


Classic Industries C10 Cluster reinstallation

The new cluster easily slid right in place and uses the six factory screws to secure it. The steering column was reinstalled, along with the wiper switch and light pull.


Classic Industries C10 Cluster lights

The new dash came right to life with nice, even lighting (something we’d never experienced in the sub) and stellar looks. The digital information screen and its rolling odometer are really cool and we’ll be putting that trip odometer to use!


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