Speedo issue - UPDATED - Help!

[Arthurdaily]

My speedo doesn't work properly - ir never has done. So, I got a new speedo head unit AND cable, checked these in a second car - all worked A1. Fitted them to my main moggy and ... no show. It works once you are over about 10 miles an hour, but essentially shows whatever speed it feels like doing. So, I disconnected it at the speedo end and went for a drive, I can see it spinning... sometimes, then it stops, then spins fast, then slow, etc... I even 'held' the spinning end and it just stopped in my hand. the cable seems perfectly fine though. I went for a 60 mile toot down the motorway (as shown on gps) but it measured only 35, then when I came off the slip road and stopped it went to 0 and didn't do anything again all the way home.

Is it possible there is something wrong 'in' the gearbox?

[lambrettalad]

If the head is fine and the cable and sleeve are ok its the worm in the box

[Arthurdaily]

Hmnn... and way of checking to ensure it is the worm gear side of things? If it IS how can this be fixed?

[Arthurdaily]

Is it a dreaded gearbox removal job?

[mike.perry]

Check cable is fully in to gear box and nut is fully tightened

[Arthurdaily]

Seems to be - plus I can't 'twist' the speedo end of the cable - but will check again.

[Arthurdaily]

Interesting I can't spin it when stationary, but can hold it still when it's moving??

[bmcecosse]

Remove the drive section from the gearbox and inspect ...........

[Arthurdaily]

Good evening BMC - which bit is the 'drive section', you mean the plastic retaining nut?

[bmcecosse]

And the drive beneath....... Most likely is that the square section socket that the square cable end fits - is no longer 'square' if you see what I mean !

[Arthurdaily]

haha... so, you undo the plastic 'nut' and then does the drive just pull out? Or is it held in at the other end?

[bmcecosse]

Pulls out..... If you have a spare - swap.

[Arthurdaily]

Hi, I have two spare gearboxes, so will swap one from there and see. Thanks BMC

[Arthurdaily]

Okay, replaced the plastic housing and the actual metal shaft with the square hole in etc. Perfect, measuring with my sat nav brought joy as it was spot on for a few miles... then... back to wobbly and no proper reading. So, home again, plastic housing back out and felt the ACTUAL work gear only to discover it spins freely in the gearbox on its shaft. Obviously when cold, and relatively dry, it 'sticks' to the shaft and is fine, once warm and lubricated it doesn't grip properly.

Any suggestions on how this can be fixed? Options avoiding removing the gearbox most appreciated ha ha

[bmcecosse]

Oh well - strip down time............

[Arthurdaily]

Bums.

Right. Is it possible for a relative novice to do this? I mean I can strip rear axles, brakes, etc now on the car - but a gearbox?!

[Arthurdaily]

OR would it be easier to swap gearboxes, I have two others, both of which the previous owners swore were good boxes...?

[charlie_morris_minor]

The fun with the minor gearbox is all the little ball bearings and springs that seem to launch themselves from nowhere when stripping the box and are fun to get back in when rebuilding.

Why not give it a go though, what have you to lose? You know what the problem is, so you know the part to replace / repair, it is not if you are investigating an issue with an unknown cause which would be more tricky for a novice, and if it works you will have gained more confidence in tackling jobs. If you fail you still have two spares to use.

[Arthurdaily]

Hi, I'm going to - but will put a spare box in FIRST to see if that works. Then I can do the repair on the first at my leisure