speedometer woes

[miketyler]

Was driving the Cuda around last night and the speedometer went haywire. It was accompanied by a noise that seemed to resonate inside the driver side fender. It sounded like the cable was trying to bind up or something. At about 40mph the speedometer then started bouncing which led to a buzzing. I looked down at it and the needle was vibrating like crazy, like a hummingbirds wings. Before I could slow down the needle broke off the hub. 



I will admit that on a rare occasion, the speedo needle would bounce for a few moments but would quickly regain its composure. So what do you think? Speedo? Cable? or both?       

[MEK-Dangerfield]

Mike,

  Unfortunately, that's a common problem. I know it happened to April. Something inside your speedo has probably blown up.


  Mike

[Chryco Psycho]

probably the cable & now both with the needle broken off the guage

[miketyler]

I may be able to mend the needle actually or just get another. The speedo seems to be working ok now, no noise and looks to be indicating correct MPH. I will have to pull the speedo to fix the needle and will ck it out. What all do I need to check for? Free and smooth spin?   

[MEK-Dangerfield]

So when you start driving, the needle will move from 100MPH down to whatever speed you are driving? If so, I think you got lucky. Maybe it was just a sticky cable that could use a lube job.  If you remove the speedo, and it looks good, I would get rid of that speedo cable real fast.


   Mike

[Katfish]

I had exact same thing happen.  Most likely it's the bushing in the back of the speedo.  Apparently it's a fairly common problem.  Mine broke the speedo needle when it happened.

It cost me $200 to have it fixed.  Fix yours before the needle breaks and you'll save some money.

[vinb]

Like Mike said you may have a dry cable, Disconnect it and slide it out and take a peek at it. If it looks questionable get a new cable , $23/24 dollars. It would hurt to take out the speedo head and inspect that also...

[miketyler]

So when you start driving, the needle will move from 100MPH down to whatever speed you are driving?

No, its indicating correctly. The pointer end of the needle broke off at the hub. What you see in the illustration is pointing at 0 MPH.

I had exact same thing happen.  Most likely it's the bushing in the back of the speedo.  Apparently it's a fairly common problem.  Mine broke the speedo needle when it happened.

Katfish - Was it the high speed vibration that broke your needle?   


Ok, its all apart. Will check the cable. What visible signs should I look for on the speedo head? As far as I can tell, it looks about the same as it did when I took it apart to put the white decals on.

Should there be any lube on the plastic worm and drive gears? Both the needle and drive movements are smooth and neither seem to have any rough spots or unusual friction points. These are pretty simple looking devices, the magnetic primary drive doesn't contact the flywheel anywhere and there is no thrust play to it but there is some on the flywheel. Also the small plastic bushing at the front has a little wear and as a result, the flywheel seems a little sloppy. Should that be a dead-nuts machine fit with zero slop?



     

[Katfish]

Also the small plastic bushing at the front has a little wear and as a result, the flywheel seems a little sloppy. Should that be a dead-nuts machine fit with zero slop?
     

Mine swung wildly back and forth and snapped the needle.  The plastic bushing was my problem.  The speedo works on magnetic coupling.  It's not a direct drive.  If the bushing is bad, there is too much play and the magnetic field will vary greatly. 

These guys correctly rebuilt mine after a complete idiot replaced the needle without understanding what was wrong..  It broke a 2nd time.

 http://www.gaugeguys.com/

They also sell the needle if you just want to replace that. 

[miketyler]

understood - mine only varied between 30-40mph (about .5") but the high speed vibration was more than the needle could take.

The primary drive from the cable is magnetic and creates a clockwise rotative field and around the needle flywheel. The needle flywheel movement and position would be directly proportional to the magnetic field produced by the magnets that "orbit" around the needle flywheel.  I wasn't sure if that much play was acceptable or not. Its all pretty delicate stuff too, the return spring on the front of the needle shaft looks like it would be difficult to reattach.

The cable is pretty dry. I was going to get some of that graphite speedo cable lube and see if it improves. If I end up having to get the speedo serviced, I will definitely replace the cable. I think I remember reading your thread about that. In your experience then, the sloppy speedo bushing causes the vibration and needle failure, not a dry speedo cable?   

[Katfish]

In your experience then, the sloppy speedo bushing causes the vibration and needle failure, not a dry speedo cable?   

That was my situation.  I actually replaced the cable first, then the speedo drive gear in the transmission.  Only thing that fixed the problem was the speedo repair.

You could go ahead and lube the cable and see what happens.  Since your needle is already broken, there's no harm in seeing what happens.  I'd check things out before fixing the needle.

[miketyler]

was able to repair the needle easy enough with a short segment of wire and a little JB-Quik. I emailed Greg Garner about some tachometer issues and asked him about the speedo issue. He said its usually the cable that causes this but also said can be caused by a sloppy head. He said to put one drop of Slick50 lube on the front bushing and thats it. He went on to say that the flywheel can be sloppy but it shouldn't be sloppy enough where it ever contacts the magnets. So I lubed the cable and the front bushing and will see what happens.

 

[Black340]

Hope that  solve the problem

[miketyler]

me too - thats a pain taking the cluster out. It's okay though. I needed to recalibrate my tach and fix my woodgrain decal at the turn singal and brake indicators. I also went and pulled all my masking tape labels I marked my wires with and replaced them with p-touch labels instead. Looks more professional.

Its fun taking care of the little stuff but I dont want to have to pull that cluster again unless I absolutely have to!     

[miketyler]

all put together and it seems fine so far. The speedo works great but at times has a very mild hop to it. I'm gonna run with it for now.