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MG MGB Technical - Speedometer not working

I have a 72 roadster w/OD and my speedometer/odometer stopped working. At first the needle was bouncing wildly up and down and shortly thereafter stopped altogether. I disconnected the cable from the speedometer. Cable is fine. Put cable back to see if I could feel it turning while moving forward - could not. However, I can feel it turning nicely when I move in reverse. Is this a symptoms of a bad right angle gear box on the transmission?
C.E. Sampson

Off the Archives it could be (in order of difficulty to cure?):

1-kink in cable,
2-cable needs greasing
3-speedo needs lubricating,
4-corrosion spot on disk/magnet in speedo.
5-the ends need to be loosened and retightened (they've got a little off centre)

Mine was Number 3.
Iwan Jones

Thanks for the suggestions. Cable is fine - I removed it for inspection and there are no problems. What I still do not understand is why the cable will turn when I run in reverse but will not turn when I run forward.
C.E. Sampson

CE - just a speculation, since I've never looked at the cable driving gear on a MGB, but several on midgets, but the gear within the transmission may be a nylon gear that is pressed onto a steel shaft. It is possible for a crack in the nylon gear to be aligned such that it will open up and slip in one direction, but tend to clamp tighter on the shaft in the other direction.

The "bouncing wildly up and down", however, is more indicative of a broken or sticky cable, or one where the square end is not locking correctly into the driving shaft from the transmission. Best of luck - - Alec
Alec Darnall

I've starting to see the same thing as C.E. - the bouncing around. Silly question: How does one grease the cable?

Rick
Rick Stevens

Pull the Right angle adapter, my bet is that you will find the square drive that goes into the transmission is broken (or perhaps hanking on by one strand. Cheers - Dave
David DuBois

Thanks everyone. I am going to check the right angle adapter today. Rick - I've been told the best lubricant for the speedometer cable (and choke cable) is dry graphite powder.
C.E. Sampson

This thread was discussed between 16/09/2006 and 17/09/2006

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