While out for a Sunday cruise in my '65 GTO, I suddenly noticed a serious flutter in the original rally-gauge tachometer needle. That little yellow pointer, which has given so many years of unwavering service, suddenly stopped fluttering, and then dropped like a cruise missile to zero rpm. The problem is that I was still doing 60 mph.
To troubleshoot the problem, I ran an external wire directly from the coil to the tach and bypassed any possible harness problems. There was no heartbeat. My engine's pacemaker was definitely dead at only 50 years old.
The question is, should I replace my original tach with another original, a repro, or a recently released new product I heard of? (More on this coming up.)
First I checked on what is available as a new reproduction single-gauge replacement. Complete reproduction rally-gauge clusters are available, but everything else in this GTO's gauge cluster is working great, so why replace it all? And why install another 50-year-old antique?
The new product I mentioned earlier is an individual tach-ometer movement, and it's made by the same manufacturer of the complete reproduction Pontiac rally gauges (and most of the reproduction hood and in-dash tachometers on the market today). It is available retail from many of the Pontiac parts suppliers who support this magazine.
This replacement tach resto part features a solid-state meter movement and plastic mounting board that fits directly into the original metal cluster housing. It allows you to remove the defunct tach, but reuse your original tach face so it matches the speedometer face and other metal instrument faces. 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 second 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, and the R&R of the dash takes several hours. But every minute, cut, and abrasion was worth it when the engine fired and the needle moved to a steady 900 rpm. (My Ram Air IV cam likes to idle around 900 to 1,000 rpm. Yeah, I confess, some of the engine internals are modified.) This '65 GTO breathed a big sigh of relief as its new pacemaker kicked to life and started monitoring one of any performance engine's most vital signs.
With the new tach in place and working perfectly, I was back to cruising without any fear of losing internal engine parts due to instrument error.
Let's see how easy this resto install is to do.
Here you can see we're driving at about 20 mph, but Mr. Tachometer is sitting on a solid zero rpm. What right does it have to quit after only 50 years of use?
1. This is the aftermarket replacement. It fits right into the metal instrument-cluster housing in the '65-'67 GTOs. The black thing at the top is the needle protector for shipping. The red wire goes from the tach to a key-on power source at the fusebox. You must use your original coil-connection wire or make your own.
2. With the needle protector out, you can see the guts of the replacement tach. The needle-protector retaining screw uses one of the screw holes that mounts the factory face plate.
3. Prior to starting any electrical work, it's a good idea to disconnect the battery. It only takes a couple of minutes.
4. We began by removing the glovebox liner to access two attachment points for the optional dashpad. There are four Phillips head screws above the gauges that need to come out, and then the pad can be pulled free.
5. To gain a little wiggle room, we removed the steering-shaft mounting bracket and let the column drop about 1 inch. It is secured by the bracket and two 9⁄16-inch nuts.
6. Here are the parts taken from under the steering column. It took only a few minutes to remove these items, and it gave us the opportunity to clean them and the area under the column.
7. To avoid scratching the paint on the column while removing the instrument cluster, we draped a small towel over the column and down under the dash.
8. Here is one of the four dashpad attaching points under the dashpad. If your GTO is not equipped with a padded dash, simply remove these screws using a stubby Phillips head screwdriver. After you remove the screws under the dash lip, the pad can be gently pulled free.
9. With the screws/pad removed, we gently pulled the housing up and out and let it rest on the towel, and then reached behind the cluster to unplug the instruments and light bulbs, and unscrew the speedometer cable from below.
10. There are three cables under the dash that operate the heater/defroster levers. They are attached to the control switches on the instrument cluster and the levers on the heater box. Here is an example viewed through the glovebox hole. We disconnected them at the heater box before trying to remove the cluster.
11. We were familiar with the wiring, but if you're not, label each wire or light bulb as you remove it. This might look intimidating, but once you start, you'll see that it's helpful and easy. Remove the cluster and heater cables carefully so you don't scratch any paint.
12. 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.
13. Several small screws hold the gauge housing to the cluster. Once we removed them, the metal case that houses the gas gauge, alternator warning light, speedometer, and tach-ometer was the next item to detach.
14. Using a small screwdriver, we removed the tiny slot-head screws holding the tach faceplate to the meter movement. Here you can see the mounting points. We were careful not to scratch the paint on the original face. Also, we did not use a chemical cleaner on the faceplates—it smears the numbers. A soft, dry cloth removed any dust.
15. With the two screws removed, we slightly lifted the faceplate and carefully moved it over the original needle and free of the meter movement. We will reuse the original face and screws on the new tach movement.
16. The factory tach housing is secured to the cluster housing with three small screws as shown. We lifted it free of the cluster and out of the way.
17. The replacement tach movement 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 fusebox, while the coil wire attaches to the stud on the left. It couldn't be simpler.
18. The original tach faceplate was carefully replaced over the needle and secured with the two factory screws. The assembly can now be reattached to the metal cluster housing and reinstalled.
19. This is one of the levers that activates 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, we lubricated all the moving parts with a quality white-lithium grease. We used Justice Brothers' aerosol grease to get into all the tight places.
20. 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. As you can see, clearance is not a problem.
21. After reinstalling all the components as they were removed, we re-connected the battery and fired up the engine. Yes! That gorgeous yellow needle jumped right up. The engine's pacemaker is alive. If we can do it, you can do it.