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Tach Attack!

Replacing a 1964-’67 GTO tach while keeping the original metal housing and Rally gauge face

Story Jim McGowan - April 26, 2012 11:30 AM

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Prior to starting any electrical work it’s a good idea to disconnect the battery. We began by removing the glove box liner to access two attachment points for the dash pad. There are four Phillips head screws above the gauges that need to come out and the pad can be pulled free.

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To gain a little wiggle room we removed the steering shaft mounting bracket and let the column drop about an inch. It is secured by a bracket and two -inch nuts.

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Here are the parts taken from under the steering column. It only takes a few minutes to remove these parts, and you will have the opportunity to clean them and the area under the column.

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In order to not scratch the paint on the column while removing the instrument cluster, drape a small towel over the column and down under the dash.

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Here is one of the four attaching points under the dash pad. With the screws removed, gently pull the housing up and out and let it rest on the towel as you reach behind the cluster to unplug the instruments, light bulbs and unscrew the speedo cable.

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There are three cables under the dash that operate the heater/defroster levers. They are attached to the controls switches on the instrument cluster and the levers on the heater box. Here is an example viewed through the glove box hole. Disconnect them at the heater box before trying to remove the cluster.

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If you are not familiar with the wiring, label each wire or light bulb as you remove it. This might look intimidating, but once you get to this point, you’ll see how easy it really is. Remove the cluster and heater cables carefully so you don’t scratch any paint.

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The original tach has the red plastic insulator on the coil wire connector. Unlike the new replacement, this is the only wire connected to the factory tach. The heater control cables are at the top.

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Several small screws hold the gauge housing to the cluster. Once you remove them the metal housing for the gas gauge, alternator warning light, speedo and tach are detached.

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The tiny slot head screws holding the tach faceplate to the meter movement can be removed with a small screwdriver. Here you can see the mounting points. Be careful not to scratch the paint on the original face. Also, do not use a chemical cleaner on the faceplate. It will smear the numbers. A soft dry cloth will remove any dust.

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With the two screws removed, slightly lift the faceplate and carefully move it over the original needle and free of the meter movement. We will re-use the original face and screws on the new tach.

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The factory tach housing is secured to the cluster housing with three small screws as shown. Simply lift it free of the cluster and out of the way.

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The replacement tach can now be secured with the original screws. The white wire is a ground that is secured with one of the tach mounting screws. It is supplied with the replacement tach. The spade connection on the right goes to the key-on power source at the fuse box, while the coil wire attaches to the stud on the left. Couldn’t be simpler.

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The original tach face plate was carefully slid over the needle and secured with the two factory screws. The assembly can now be reattached to the metal cluster housing and re-installed.

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This is one of the levers that activate the heater box controls. They are made of plastic, which becomes brittle with age. We repaired a broken connection point with Super Glue and JB Weld as seen at the bottom right. While the assembly is out of the car, lubricate all the moving parts with a quality white lithium grease. We used Justice Brothers aerosol grease to get into all the tight places.

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To show that the replacement tach fits exactly as the original, here’s a profile of the tach on the left and the temp and oil pressure gauge connections on the right. No clearance problem here.

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After reinstalling all the components as they were removed we connected the battery and fired the engine. YES! That gorgeous yellow needle jumped right up. The engine’s pacemaker is ALIVE, ALIVE! If we can do it, you can do it!

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This is the aftermarket replacement. It fits right into the metal instrument cluster housing in the ’64 to ’67 Pontiac GTO/LeMans. The red wire goes from the tach to a key-on power source at the fuse box. You must use your original coil connection wire, or make your own. The black thing at the top is the needle protector for shipping. The needle protector retaining screw uses one of the screw holes that mounts the factory face plate.

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You're cruising along and notice a serious flutter in the tachometer needle. Oh no! It's a 12-volt embolism in a wire, an electrical clot, a TACH ATTACK!

That little yellow needle, that has given so many years of unwavering service, stops fluttering and drops like a rock to zero rpm. The problem is you’re still doing 60-plus mph. The pacemaker is dead at only 46 years old.

 Now, should it be replaced with another original tachometer or with a new product with upgraded internals? After some soul searching about original parts, we checked on what’s available as a new reproduction single gauge replacement. Complete reproduction Rally gauge clusters are available, but everything else in this cluster is working great, so why replace it all?

 And why install another 46-year old antique? We found an individual tach replacement that is being made by the same manufacturer of the complete reproduction Pontiac Rally gauges, as well as most of the reproduction hood and in-dash tachometers on the market today. 1964-’67 GTO tachs are available from Just Dashes in Van Nuys, California.

 This replacement unit features a solid-state meter movement and plastic mounting board that fits directly into the metal cluster housing. It allows you to remove the defunct tach movement, but re-use your original tach face so it matches the speedo and other gauges. This is important as all these gauge faces have aged and faded together. A bright new face would stand out in the crowd. It features an exact duplicate of the original tach needle, so when it’s assembled, it looks 100 percent original.

The new tach movement has three connections on the back. One (the red wire) goes to a key-on spade in the fuse box and the other connects to the coil, just like the original. A white ground wire is used from the back of the tach to the metal housing. It couldn’t be simpler.

 The installation into the cluster literally takes a few minutes, but the repair and restoration of the dash takes several hours. But every minute, cut and abrasion was worth it, since the engine fired and the needle moved as the Ram Air IV cam likes to idle around 900 to 1,000 rpm. This ’65 GTO breathed a big sigh of relief as its pacekeeper kicked to life and started monitoring one of the engine’s most vital signs.

 With the new tach in place and working perfectly, we were back to cruising the GTO without any fear of losing internal engine parts due to instrument error. But driver error is still always available!

For Your Information:

Just Dashes (800) 247-3274

www.justdashes.com

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