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MG MGB Technical - speedometer drive?

I broke rule #1 today (#1 Don't mess), and decided to change the speedo cable, as the needle had developed an annoying wobble.

Glossing over the unbelievable difficulty of changing the cable: a 10 minute job that takes an hour, I now have a seriouly under reading speedo (It slightly under read before, now it is much worse).

It shows 15 mph at 30, but seems to catch up again at 50 mph.

My thoughts turn to the gearbox end, having had the speedo head apart before, and found nothing wrong.


I have the type L.H. overdrive.

According to my manual, the output shaft speedo drive gear is sandwiched between the two bearings with spacers, so provided the output flange nut is tight, it can't slip.


Is it a solid gear, or a plastic outer glued to a steel centre? (I had a jeep once where the plastic outer gear came loose, I was able to glue it back on with epoxy.)

If I remove the speedo drive tube and small gear, will oil pour out? (I'm thinking that gear is loose, or has a tooth missing)
Martin Layton

gooday martin. on my 69 with od, its nylon. no trouble removing it with oil etc. easy job, 5 minutes.
Cactus

Cheers for the reply. I removed the drive, (with the back jacked up- no oil comes put) and the gears are tight and complete. The cable is definitely driving, so it must be the speedo head, I will have to get a spare and try it again.
Martin Layton

I had the same problem. In my case, I 'thought' I had lubricated the cable and removed any kinks...but I was wrong. The cable is really sensitive to sudden bends -probably the reason why they thought of the angle gear in the first place.
Philip

This thread was discussed between 03/03/2007 and 10/03/2007

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