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MG MGB Technical - Speedo Disassembly

G'day. Has anyone got a link to instructions on how to take a speedo apart on my '69 model. My main problem is how to get the reset cable for the trip meter out of the case. I have got the glass off and the two screws holding the thing together off, but I can't fiddle the cable through the hole.

Tony
Tony Oliver

Tony, I have forgotten the details but I believe there is an article on a Sunbeam Tiger website. You should find it with Google.
There is a very small pin in the shaft which you push out allowing the knob to be pulled off

Terry
T J Malloch

There should be, but I searched and searched on my 73 but just couldn't see one. Eventually I managed to get the guts out of the case with the cable still attached. However when I went to put it back the needle pinged off. Fortunately I didn't lose it and it didn't break the spindle, so I safely supported the car with one rear wheel off the ground, did my calculations, set the revs to give 30mph in 4th, and popped the needle back on.
Paul Hunt 2

my car is a 75 and and may be different.
The small plastic reset cable end just slides onto/off a square projection of the the mechanism when the mechanism is being put into the case. Once removed this leaves the little cable still attached to the case by a press snap fitting.
Try wriggling the small cable as you gently pull the mechanism from the case.
You can see the square drive in the top corner of one of the photos

http://mywebpages.comcast.net/rhodes/speedo.pdf
Peter

Thanks Gents. I can see the little pin. Got it apart. Drive gear to trip meter is split and was jamming the drive. If I can't get a new gear I will just use it without the trip.

By the way, does the angle drive of the gearbox simply turn the drive through 90 degrees or does it have a ratio change to the drive cable.

Tony
Tony Oliver

It's just an angle change, as some cars had one originally (RHD) and others two (LHD), and it works exactly the same with none. The gearbox one can be deleted if you substitute a slightly longer cable, much cheaper than replacing the drive, neither of my cars have them now. Really LHD cars should keep the top one as it avoids a tight turn in the cable due to limited space, something which isn't a problem underneath.
Paul Hunt 2

Thanks Paul, I am having problems with the angle drive. It was slipping when the gear jammed the speedo as mentioned above (which was handy otherwise the cable would probably have twisted and snapped) so I will just put the cable straight into the gearbox. It is long enough but I didn't want to do it in case the angle drive was an essential part of the system.

Cheers

Tony
Tony Oliver

This thread was discussed between 14/10/2007 and 15/10/2007

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