New speedo right angle drive/cable lasted < 1mile!

[markc555]

I fitted a new speedo cable (complete inner and outer) and right angle drive but the new combo has lasted less than a mile What could I have done wrong?

I removed the centre console etc to fit the new cable and drive from above. While in there there I fitted a new foam noise/heat insulation pad. The old cable and drive came out easy enough and revealed that the gearbox end of the drive had snapped off. The new drive didn't seem to locate very positively but I was able to tighten it up and all seemed well. Routed the new cable as per the old one and put everything back together.

It was a P.I.T.A job, especially squeezing the new unformed pad back under the gearbox cover, and I'm not looking forward to doing the whole thing over again

The car is a '69 LHD S2 FHC and the new cable and drive were supplied by SNG Barratt.

Cheers

Mark

[iani]

First remove the cable from the angle drive, if the cable is still intact remove the angle drive. I bought a new angle drive recently and it failed within a hundred miles or so, the shaft that went into the gearbox had unwound and it was replaced under warranty.

Ian

[christopher storey]

The speedo head ( or the mechanical gear drive to the odometer ) seizing up is a common cause of this problem . What then happens is that the square section in the angle drive, which is really just another piece of speedo cable, then unwinds and becomes shredded. The first thing I would do is take your speedo out and using a square ended piece of cable ( or failing that a small screwdriver ) see whether the inner drive part moves freely, sufficient to turn not only the speedo disc but also the odometer gearing. A clue to a fault in the latter is if the breakage has occurred when two or three figures were being turned over together, e.g. at the transition from 099.9 miles to 100.0 miles

[markc555]

Took the speedo out yesterday and it is indeed partially seized/very stiff.

Thought I'd have a look inside for myself and found this useful guide...
http://www.tr3a.info/PDFs/speedo.pdf

After removing the bezel, glass, pointer and face I took off the odometer and trip mechanisms. The problem appears to be with the worm gear that is driven from the input shaft. This gear increments the odometer and trip mechanisms.

I gently levered out said worm gear shaft. There was no obvious problem other than plenty of black gunk in the gear teeth and on the shaft. My best guess is that this has come from a partially disintegrated gasket that seals the back case of the speedo where the "clock" mechanism is screwed to the case. could be heat or old age or more likely a combination of both.

I've put the components in carb cleaner and will attempt reassembly tomorrow.

I suspect it will have broken the right angle drive but I'll get to that later, maybe next weekend.

Cheers

Mark