Dodgy speedometer

[DaftMule]

I have an interesting intermittent issue with my speedo.  Sometimes it registers the wrong speed and gradually gets more out of whack as I go along.  Other times it just doesn't work at all.  Most of the time it's fine though but I have noticed that it moves in a fairly jerky manner pretty often.  

In all cases, if I pull to a standstill (e.g. at a junction or traffic lights) then pull away, the speedo starts working correctly.

Not sure if the speedo is mechanical or rigged to a gearbox sensor?  Anyone else hav or had this issue?  

[Old Peter]

Hi Adam, 

I have not come across this unusual issue on a car before, although I did have to change a motor cycle cable in the sixties.

I have tried to find out out about sensors, and with the modern auto gearboxes I would guess that a sensor might be on the ZF gearbox.

There will be some members who will be quite exact  ii I don't get underneath cars any more.

Let us know how you get on.

Reards

Peter.

[JOC Admin]

I have seen this before with worn speedo drives (if mechanical or electro-mechanical) and/or worn gearbox bearings which can produce spurious results.
Easy to diagnose by removing any mechanical speedo drive from the gearbox and examining it for wear

[Guest]

On ‎11‎/‎6‎/‎2018 at 11:03 PM, DaftMule said:

I have an interesting intermittent issue with my speedo.  Sometimes it registers the wrong speed and gradually gets more out of whack as I go along.  Other times it just doesn't work at all.  Most of the time it's fine though but I have noticed that it moves in a fairly jerky manner pretty often.  

In all cases, if I pull to a standstill (e.g. at a junction or traffic lights) then pull away, the speedo starts working correctly.

Not sure if the speedo is mechanical or rigged to a gearbox sensor?  Anyone else hav or had this issue?  

New to S-Type, but does the speedo operate off one of the ABS sensors?