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Speedo stop working


tonyl999
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The speedometer on my Mk3 GT6 has stopped working. I haven't started looking properly yet but can anyone advise -

 

- what's the best way to get at the speedometer? It's really tight behind it to try and get at the retaining screws or speedo connection. Can I get at the back of it by removing the centre panel on the dashboard?

 

- can I get at the gearbox speedometer drive connection from inside the car by removing the gearbox cover?

 

- finally, if I can get to both ends of the cable and it needs replacing is it straight forward from there on?

 

Any help much appreciated.

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tunnel out to get at the drive end

if you have overdrive the angle drive on the gearbox can shear its drive.

 

cant advise on GT6 panel removal 

 

if the cable inner appears ok but short you can get some grips on the outer  and  rotate to wind the spiral to make longer or shorter outer case 

for more inner protrusion

 

if fitting a new I suggest some added lube,  should be dry use graphite dust from a sandpapered pencil on the inner but stuff like vaseline will work OK

you dont want any runny stuff or it will transpose up the helix into the head

 

Pete.

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Has the car got overdrive? if so the angle drive would be top of my list of suspects....If that has broken it may be down to the cable, or even the speedo itself seizing. The drives are expensive (and there were lots of rubbish ones around) so you will not want to do that job twice.

 

Access through the centre panel will help a lot. You may end up taking the rev counter out too, though on GT6 that has a cable drive too. 

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Not complicated, teh overdrive just means it has an angle drive as well as the speedo cable. It is just pop the tunnel out (I said that quickly!) and find out which component has gone. If the angle drive, also replace the cable as a matter of course, and check the speedo isn't seized (unusaul)

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Yes, access through the centre panel. The way I've done it in the past is undo the rev counter mounting thumb wheels via the centre panel. Then undo the rev counter cable from the dizzy and pop out the rev counter from the dash. Then you can get at the left hand speedo thumb wheel. The right hand one is accessed through the right hand parcel shelf. Then pop out the speedo. Fairly easy to undo, a bit trickier to get back.

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Speedos on all our cars always seem to end up needing bat-like inversions of the head and shoulders into the foot well and contortions worthy of a circus act. It is also axiomatic that the square drive on the cable will never quite match up with the hole in the speedo drive and slot in nicely by touch, and the collar never quite lines up nicely on its thread, so you end up removing the unit and re-fitting it with the cable attached, having fondly imagined that you could do this "little job" seated in the driver's seat...

 

Like Clive, my favourite culprit is the angle drive, which is, especially in repro form, a horrid little piece of engineering. I once returned a brand new one to Rimmers that came out of the box jammed solid, so if replacing, check it works before fitting. Also, check the cable (if intact) is turning really freely in its liner. If it has "wound up" it will feel gritty with tight spots.

 

One tip for restorers putting cars back on the road after the (inevitable) lengthy restoration, is that speedos dry out long-term storage, and can emit a squeak that for all the world sounds like a suspension issue, until the speedo cable winds up and snaps in protest at trying to drive a semi-seized unit. A dash of WD40 on reassembly works wonders!

 

Steve C

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one way out to elliminate  the angle drive is to cut a hole saw in the tunnel/floor use a longer speedo cable  and run it inside the car up to the dash

 

make sure the hole is alligned ok before you hole it  , fit a grommet to seal and its good for years ,  how you run it up is down to choice

 

preferably not under your feet !!

 

Pete

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