TR3A Retrofitted Jaeger Tachometer

I may have lost a little sleep thinking about how I was going to get functioning instruments in the car. One of the bigger internal arguments towards retaining the original engine and transmission was so I could enjoy the action of the original, larger than life Jaeger speedometer and tachometer. You see, the TR3's original Jaeger Tachometer is driven mechanically by a cable from the engine's distributor. Since the Miata engine neither has a distributor nor tachometer cable, it wouldn't be compatible. I researched instrument suppliers and most of the aftermarket stuff available wasn't as large and certainly didn't have the character or "the look." While taking a break from the engine install I decided to crack open the Miata's instrument pod. There I discovered that the tachometer was a serviceable part, that is to say that it is removable as a whole unit. Well, well, well...
                                    
On the left is the Miata tach removed from the pod. On the right, the original TR3 unit out of it's cup. Similar in size, eh?

I  removed the electronics from the Miata tach face and matched them to the TR3's. The unit attached the same way as the mechanical one did, two screws through the front. The screw holes were in a slightly different location so I drilled a new set of screw holes in the TR3 gauge face to match the Miata mechanism. Voila! The Miata mechanism- electronic tachometer that is triggered by the Miata engine computer- is attached to the classic original Jaeger gauge face. All that was left was to add the appropriate power, ground and signal wires. I insulated the inside of the original TR3 tachometer cup and installed the electronic works. I even painted the Miata needle to match.

The best part is that it works flawlessly and you'd never know. Now, what about the speedometer? the 1994 Miata donor car was among the last year of mechanical cable driven speedometers. That's a YAHTZEE! I was able to use the Miata speedo cable and just graft on the TR3 cable's end to screw it on to the speedometer.

No more sleepless nights worrying about weird looking or inappropriate master gauges. When looking into the cockpit, or generally looking around the car there is nary a clue of the sleeper engine under the hood.

 Here is the back side of the center instrument pod. As I noted in an earlier post, all switches were rust seized. The center instruments were in very poor condition.

 On the left is the electronic mechanism. on the right, the mechanical.

 Extra set of screw holes for the electronic unit. The original ones were later filled in and blended away.

 No explanation needed.

 Insulated cup with wires protruding out the back.

 assembled with Miata needle painted to match original.

Not a great picture, but shows overall the final product. As I drive the car I don't even think about it, it just works! Also note in this shot the slightly relocated shifter.