bouncy speedo!

[Kevincolley]

greetings all,
got a small problem with the speedo on my Van, it works, but it bounces all over the place, and sometimes it just sits on the rest pin, ive changed the cable and oiled it, ive tested the speedo on my other morris and its not that, ive checked the nylon gear just inside the gear box and thats fine, i just dont know what else it could possibly be. any suggestions or advice would be greatly recieved

[bmcecosse]

It HAS to be the cable - or the gearbox drive....It's 'possible' that the scroll inside the gearbox may be slack....not something you want to hear of course, so double check everything else first.

[katy]

The cable may be slightly too long or too short. Try loosening the big nut that holds the cable housing onto the speedometer and see if that makes a difference.

[Boomlander]

Almost certainly the inner cable snagging or rubbing on the outer sleeve then releasing causing a sudden surge from the needle and then dropping the needle to zero when it snags up again.

[Mog-nuts]

If you remove the nylon gear speedo drive you can just get your finger

through the hole in the side of the box and feel the worm drive on the third motion shaft.

If you can turn it with your finger, that's your problem found.

Gear box out then I'm afraid.

[Little Blue]

So... it's not meant to do that?
Mine has always bounced around like crazy. I've gotten used to it and can read it fine... would be nice to fix it though!

[chesney]

It's odd, in my 61 saloon the speedo rocks around with seemingly no direction, yet in my 68 saloon the speedo is rock steady, despite the fact the 61 has a brand NOS cable, and the 68 the original!
I guess it comes down to wear in the nylon speedo drive, oil in the cable itself,any trace of oil in the speedo (on the drag cup etc) and general wear of the speedo. On my 42 Ford GPW jeep we used a NOS speedo and cable in a rebuilt gearbox, and that writhed around madly, but a patient dribble of 10/40 motor oil and a high wall to stand on did the trick, and that read steady as a rock too.

[Chipper]

My Traveller's sometimes also sits on the stop for quite some time (although the odometer carries on working), then randomly springs back into action after a few miles, then it's fine after that!

[Gareth]

Bit late to the party on this one, but I had exactly the same problem on Phyllis. Her needle had bounced for the whole time I've owned her although I'd noticed it getting worse in recent months. I didn't do anything about it, rather than just live with the bounce.

Until I noticed that the odometer had stopped working - there is a fault where the odometer can stick as it turns which results in it a) not counting miles accurately and b) adding extra resistance to the cable, thus causing the regular needle-waver, or worse, 'bounce'.

I replaced the speedo with an overhauled unit and the problem went away, so it could be something to look for. Granted, the cable is usually the first port of call but if that doesn't appear to be the problem, you might need to investigate the inner workings of the mechanism.

[myoldjalopy]

My speedo needle swung up and down until one day there was a loud shrieking/grating noise and the needle stopped working altogether. The cable had broken so I fitted a new one.The needle was then steady for a while but has returned to swinging - at about 60mph it oscillates between 40 and 80! I see it as part of the charm of the car
Pete

[mike.perry]

It is part of the charm until you pass a speed camera whilst trying to work out what your speed actually is

[Boomlander]

It's worth fitting a new cable as they are inexpensive and simple to fit - worked for me!

[dawpooldad]

Hi,

Re bouncy speedo needle, I tried all of the above on our 1954 Ser 2 with the old jukebox style dash. All to no avail. It was only when I took out the speedo head and dismantled it, that I found the problem.

I found the drive to the Odometer was almost, but not quite seized, thus causing the spiral drive to wind up the speedo cable (which is just one long spring) before releasing itself. Being driven by the same drive, it then caused the needle to fluctuate. The tell tale sign was the wear dust on the fibre drive gear and it being in the same place on the gear.

A squirt of the ubiquitous WD40 cured it temporarily until I plucked up the courage to dismantle the complete shaft and clean and lubricate it properly with some nice new lithium based grease. It wasn't easy but with care, it is doable.

If you think about it, the original grease was eons old and was bound to harden over time. We grease everything else on a regular basis, but not the speedo head, whichever model or age of Moggie you have!

It was after this incident that I found a NOS head at an auto jumble and I was able to compare them and guess what....... the grease was solid!!!!

So even if I'd have fitted the new head, I possibly would have had the same problem!!

Hope this helps,

Best Rgds

dawpooldad

[airsniper]

If the speedo cable is anything like the one on my old Triumph motorbike - dont grease the last 6" near the clock. I did and it got into the speedo workings and clogged it up.

[ianmack]

As well as lubrication it is worth checking the routing of the speedo cable. Sharp curves can also give erratic movement.