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MG MGB Technical - Not really new! Speedo MGB'72

Hi,

I have read all the stuff about skinned fingers, etc.....

Unfortunately mine has stopped - and I got a speeding ticket.... so, maybe time to do something.

Basic question - reading the various threads it isn't clear to me that you have to take the cable out at both ends. It seem from some posts that you can feed a new one in from the dashboard side. I ask because I put it up on the ramps and the gearbox endis behind a chassis member!!

TIA Barry
B Mahon

Assuming that the inner cable is intact, it can be pulled out from the dashboard end.

If it's broken that probably won't be possible.
Dave O'Neill2

It's the removable cross-member though, so four bolts and lowering the back of the gearbox on a jack might give you better access from above.
Paul Hunt

Barry. The cable is one possible reason for the speedometer to quit working. Angle drive at the rear of the tranny, the plastic gears that drive the angle drive, and internal problems with the speedo are other reasons.

Disconnect the cable at the speedo and move it to where you can see the inner cable. Put the rear of the car up on jack stands, then start the car and put it in gear. Look at the inner cable and see if it is moving. If not, it has either broken or has become disengaged from the angle drive. If the cable is not moving, put the car in neutral and turn the end of the inner cable with your fingers while pushing it into the outer sheath. If you feel some movement it may have seated the cable into the angle drive. Repeat the experiment. If you still have no movement you know the problem is with the cable, angle drive, or drive gears.

Remove the lower cable attachment from the angle drive. You many have to drop the tranny crossmember, but I have not had to with non-overdrive transmissions. Pliers may be required to get the cable housing to break loose from the angle drive. Remove the cable and examine. If the cable is broken, the situation is obvious. If not, examine the ends to make sure they are square and check the fit of the lower end into the angle drive. If the cable fits into the angle drive, start the car, engage first gear and look to see if the angle drive is turning (a flashlight and a mirror may be required to do this depending on the angles involved). If the angle drive is turning, the cable is the most probable cause of the problem. If it is not, it is either the angle drive or the gears inside the transmission. Stop the engine, remove the angle drive from the tranny and repeat the experiment looking at the take off point for the angle drive. If it is turning and the angle drive output end is not turning, the problem is the angle drive.

With the standard transmission, the overdrive cable may be used, without the angle drive, according to some. Have not done this myself. But, angle drives are becoming more difficult to find, hence, leading to people experimenting with a standard tranny, OD cable, and direct attachment of the cable to the tranny.

New cables arrive without lubrication and, if you do not remove the inner cable and lubricate it, failure will happen quickly. Grease, such as white lithium grease, works on the inner cable.

If you do not have a speedometer, you can drive using the tachometer. You can either figure out engine rpms vs speed using the figures in the factory workshop manual, or use a GPS and note what the tachometer is indication at various road speeds. Good thing to know anyway as higher indicated engine speeds at any standard road speed, can indicate the clutch is beginning to slip.

Les
Les Bengtson

This thread was discussed between 13/05/2014 and 14/05/2014

MG MGB Technical index

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