TyCor

HELLO...

I have my Speedo and Tach removed and and now have some basic mechanical questions.


On the Tach...
The Tach did not work when I got the car. Where is the harness located that hooks into the back of the Tach??? I cannot find it anywhere. Below the Pic of the Tach is the 3 wires I found "entwined" around the wiring bundle...the wires are brown, red, and black; do you think someone but the harness off????
After I get some traffic on this question, I'll ask about the speedo, I think it is easier to answer.

ccs96

I think that's your tach connections; pink, brown and black.

TyCor

Yes...I think someone cut the harness off...does anyone know where I can find a new one?

I'm Batman

New, I don't know. I bet a lot of Corvette breakers would have a junk harness that could donate a pigtail.

TyCor

Thanks, at least I think I now what I am looking for now.

Next part of the question....

What is the long "barb" on the back of the speedo? What does it do?

0Willcox Corvette

You could just run new wires to the tach!

The positive wire is a switch voltage from the ignition switch. This would be the wire that attaches to the top left terminal in your picture (or passenger side if installed in the car).

The ground wire is a common ground you can pick up from the center gauge cluster and it attaches to the right hand terminal in your picture (or driver side if installed in the car).

The signal wire comes from the tach connection on the distributor, pass’s through a tach filter and then in to the car and attaches to the bottom single terminal in on the back of the tach!

I’ll have look around the shop tomorrow, maybe we have an old harness we can snip the ends from, but if not you can hardware this and it will work just fine.

Willcox Inc

TyCor

That would be outstanding if you had a spare harness. Of course I would intend on paying you for it.

can you explain the speedo set-up...when it was hooked up, the speedo needle would "bounce" slightly as I drop at low speed, and make a rubbing sound...could that be the cable or the gears inside the speedo??

0Willcox Corvette

Just to add to this post; I did not notice the cut wires in the first picture.

I think before I hardwired the car, run a continuity test from the tach wire to the wire in the dash. Test the black wire to see if it’s a verified ground and test the hot wire to see if its 12 volts switch. If all test out ok, you can lengthen the wires to the tach and you are good to go!

You can check the tach to see if it’s working by hardwiring it with the tach out of the car.

Again, run 12 volts to the passenger side wire, run a ground to the driver side upper and run a wire from the pulse terminal to the distributor. The tach should work and function if all is good.

If the tach is good you are set to go, if not email us we do have the boards in stock and, our tach boards are pre-calibrated and very easy to install!

Willcox Inc

0Willcox Corvette

You’re posting faster than I can type!

The noise you are hearing from the speedo and the bouncing could be caused by the speedo cable or the speedometer head! It’s hard to say without having it here.

If you send it in we can test it for you, it’s free and will only cost you the shipping.

The issue is that it’s out now and putting it back in only to find out the cable was not the problem would be a real pain.

One question for you, was the odometer working on the speedometer? If not then it is in need of repair.

TyCor

basically, i bought the car, drove it for about 10 minutes right into my garage and began tearing it apart. the speedo needle did work, but I do not recall if the odometer worked.

I'll take another look at it in the morning...can you tell me what that other black extension is that is attached to the back of the speedo?

thanks for all the help!!

TyCor

I just used a drill to check the speedo, and YES, the odometer and speed needle work. I think I have a bad cable. to replace the cable, do I remove the old cable assembly, or just the actual cable and leave the sheething in place?

0Willcox Corvette

While the speedo may work fine with a drill, it can still be the culprit. If replacing the speedometer cable, replace both the cable and the case.

If you can, check the end play (run out) on the speedometer first worm and magnet with a micrometer. It would not be unusual for either the cable or the head to need service.

Use your fingers and see if the first worm and magnet have side to side play. You can do this right at the place where you see the collar on the back. There is a brass collar with a metal shaft that is flared over. The metal is the end of the first worm and magnet, the brass collar is what holds it in place.

If it feels loose as can be, in and out and side to side it might need the main bushing replaced in it. For now though I would just see what the end play is, replace the cable and email us direct at Willcox@willcoxcorvette.com .

What ever you do, don’t put regular grease on the cable and install it back in the car. The cable is reverse wound and this will push the grease up the cable and in to the speedo first worm and magnet bushing. This oil impregnated bushing won’t tolerate lubrication and the excess lube will allow dust to collect on this bushing and inside the speedometer causing early failure.

In short, greasing cables keeps us in the speedometer repair business! It packs the heads full and then we get to clean them out and install new bushings!

Willcox

TyCor

What's the difference between a 40'', 72'', and "lower" speedometer cable??? which one do I need, and do they come with the sheething and cable?

Theiskell

That is your odometers trip/reset

Theiskell

For the connections on your tach you could just put female spade connections on your existing wire and plug them in as long as they check out. I just done a tach conversion on mine and I didn’t use a stock connector. I could get you a picture if you need it I haven’t put it back in yet.

TyCor

I don't think I need a picture, I have an idea of what you are talking about. Before I remove the speedo cable, how do I know how long of one I need?

TyCor

How do I know which length speedo cable to by??

Theiskell

Not sure, I am at work at the moment, but when I get home I can measure for you.

0Willcox Corvette

0277 1969-1977 Speedometer Cable is for 1977 with MT and no cruise control.
36692 1969-1977 Speedometer Cable. Lower W/AT 69-77
0263 1969-1977 Speedometer Cable. Upper W/AT 40" 69-77
36696 1977-1982 Speedometer Cable. W/Cruise - Lower 77-82
36695 1977-1982 Speedometer Cable. W/Cruise - Upper 77-82

I tried to clear this up on the site today before I answered you. We needed more details on these cables so I fixed it. I hope this is better now.

Willcox

TyCor

I am sure this will become obvious when I get under the car to disconnect the cable from the tranny, but what is the difference between a lower cable and upper cable?