67 Tachometer 'sticky' needle?

[Alexander D.]

What would cause the tach needle in my '67 coupe (base engine) to 'stick' at a given RPM?

For example, when I start the car it accurately shows the idle RPM. Sometimes when I accelerate the car the tach needle may act normally and rise and fall with engine speed. But sometimes the needle will 'stick' at a given RPM and not follow engine speed as it should. If I turn the engine off the needle will momentarily stay 'stuck' before dropping back to zero. At other times if the needle is stuck at a given RPM i can 'unstick' it by revving the engine beyond the 'stuck' RPM. The needle will then move up to read the proper RPM and act normally, at least for a while.

I had the distributor rebuilt with a new tach gear a couple of years ago after the old tach drive gear galled up. I also removed the tach cable to lubricate it when I installed the rebuilt dizzy. Soon after the tach started acting erratically and while checking things I noticed that I had inserted the tach cable backwards. So, I put it back in the correct way but the sticky behavior has continued on and off since then. I read somewhere that the tach end of the cable has a circular (brass?) thingy around it to stop lube from migrating into the tachometer instrument. So, is it possible that some crud got into my tach head and gummed up the works?

Is there anything I can do to free up the tach needle at this stage?

Thanks for your advice on this 'sticky; subject!

[Donald O.]

Re: 67 Tachometer 'sticky' needle?

Alex,

First thing to do is to call Joe Ray and sl for his expert advice

To debug the tach you will have to remove it from cluster. Unfortunately, this means you'll have to remove the cluster from the dash first

Then send the tach and speedo, together, to Joe Ray for repairs, restoration, recalibrating.
Joe Ray
2025 Cedar Creek Rd
North Little Rock, AR 72116
1-501-680-4740
email vettenut0071946@att.net

Install new speedo and tach cables. Get the new speedo cable from:
John Rullo
Deluxe Speedometer Service
2330 S. Kalamath St. Unit A
Denver, CO 80223
1-303-629-6958
1-800-907-6505

https://www.speedometercablesusa.com

Don

[Alexander D.]

Re: 67 Tachometer 'sticky' needle?

Thanks Don for the recommendations on who can repair the tach, and where to get a tach cable.

Taking out the cluster isn't a simple operation. I was hoping that there might be something that could be done short of that to fix the sticking tach needle. I'll live with it as it is until the fall when driving season is over when I can tackle the cluster re & re project.

[Alexander D.]

Re: 67 Tachometer 'sticky' needle?

Last night I dove into the task of replacing my tach cable assembly in hopes this might solve my erratic tachometer issue. For years my tach hasn't worked properly, if at all. The needle would 'stick' at random RPM's, or fail to rise past about 10k. Reaching under the dash to loosen the cable ferrule would sometimes free up the needle, only for it to get stuck again soon after. This made me suspect the cable might be binding inside the cable sheath. Of course, if it turned out to be the gauge, then I would have to remove the cluster and send it in for repair.

I read all the threads on instrument cluster removal, and how little room there is for fingers to do anything back there without at least moving the cluster out a precious inch or two. I didn't want to drop the steering column, etc. so just basically got stuck wondering what to do. It was either bite the bullet and take the cluster out for restoration, or take a stab at replacing the tach cable and sheath in hopes that might fix the tach.

Last year I bought a tach cable assembly with sheath from LICS (Part # 37-158 Tach Cable 64-67) but never got round to installing it, until last night.

My first task was figuring out to remove the firewall grommet the tach cable goes through on its way to the cluster. After some cussing, I managed to extract it from the engine side without tearing it. Next, under the dash, there was just enough room to carefully get my fingers up behind the cluster to undo the old cable from the back of the tach. Rubber gloves gave me enough grip to undo the ferrule After undoing the cable sheath from the distributor. I pulled the cable and sheath out through the firewall. Getting the new cable with sheath threaded from the distributor through the maze of wires along the firewall, then into the passenger compartment was "fun". Luckily, all went well. After tightening the cable connectors at the dizzy and the back of the tach I took a deep breath and started the car...

IT WORKED!!!!! The tach now operates normally! What a joy to see it rise and fall with engine speed!

So, the issue was the tach cable assembly, after all. The engine side of the old cable sheath was very stiff. Perhaps the sheath had shrunk into a position that moved the cable out from the back of the tachometer. Not sure. The cable itself wasn't broken.

What I learned is that it IS possible to replace the tach cable and sheath without moving the instrument cluster at all. Yes, it's very tight up in behind the dash. You need to be careful to not dislodge the cluster illumination light sockets. Two of them came out while I was fiddling up there, including one at the top of the tach gauge, which was very hard to get back in. I managed this delicate operation using a pair of... chopsticks!

Hope this helps anyone with a 'sticky' tach needle.

[Bill M.]

Re: 67 Tachometer 'sticky' needle?

Alex while you are at it you should check your gear that goes into the distributer. I found my not only the pinion gear but also the shaft gear on my distributer all chewed up. I think the gear damage was caused by my cable binding.

[Alexander D.]

Re: 67 Tachometer 'sticky' needle?

Alex while you are at it you should check your gear that goes into the distributer. I found my not only the pinion gear but also the shaft gear on my distributer all chewed up. I think the gear damage was caused by my cable binding.

Good point Bill. I had my distributor rebuilt a couple of years ago after it had chewed up the shaft gear and the dwell was wobbly due to internal wear.

All seemed okay when I installed the new tach cable last week. I didn't see any tell-tale metal filings, so I'm hoping everything is still okay in there.