Faulty Speedo Drive

[Geemccaw]

Hey guys,

Replaced my speedo drive today as I suspected it wasn't working. When you spin the wheels the speedo drive does not rotate. Is this a fault from inside the gearbox? (Iv tried 2 and both are the same)

Cable moves the needle when you spin it by hand so that's not where the issue lies.

Any info would be great

Thanks 

George

[ChrisRLewis]

Perhaps it is the speedometer drive cog on the gearbox mainshaft that is worn?

[Geemccaw]

Perhaps it is the speedometer drive cog on the gearbox mainshaft that is worn?

Would this be visible without removing he whole gearbox? Or is that the only way I would be able to check?

Also do you know if that is available as a replacement part? 

[Rusty's Uncle]

If the cable and speedo drive are all ok then a Chris says you are not getting drive from the gearbox . However I would think that it is highly unlikely that the large drive gear at the back of the gearbox is worn. It is more likely that the ball bearing that transmits the drive from the main shaft has been omitted . I have never tried it myself but it may be possible to disconnect the main gearbox mount bolts, lower the gearbox end and get access to the rear casting.


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[Geemccaw]

If the cable and speedo drive are all ok then a Chris says you are not getting drive from the gearbox . However I would think that it is highly unlikely that the large drive gear at the back of the gearbox is worn. It is more likely that the ball bearing that transmits the drive from the main shaft has been omitted . I have never tried it myself but it may be possible to disconnect the main gearbox mount bolts, lower the gearbox end and get access to the rear casting.


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Thanks for the advice! We did manage to drop the end of the gearbox while changing the speedo drive over. So I'm sure it's a possibility. Do you have a link or anything for the bearing I would be after? Are they easy to replace? Would be nice to know how fast I'm driving for once haha

[Rusty's Uncle]

I am in southern Spain until Friday but I have a gearbox in pieces on my table at home so when I get back I can show you what to look for.


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[Geemccaw]

I am in southern Spain until Friday but I have a gearbox in pieces on my table at home so when I get back I can show you what to look for.


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That would be amazing! Thanks for the help 

[Rusty's Uncle]

Got back last night , got the bits out and took a picture then realised that I could not attach it. So I have the parts in front of me. The main shaft has a dimple in it where a ball bearing sits (5.5mm) the speedo drive worm gear has an internal key way which slides over the ball to get the drive. If the gear is turning on the main shaft then I suspect that the ball bearing was omitted.

[Geemccaw]

Got back last night , got the bits out and took a picture then realised that I could not attach it. So I have the parts in front of me. The main shaft has a dimple in it where a ball bearing sits (5.5mm) the speedo drive worm gear has an internal key way which slides over the ball to get the drive. If the gear is turning on the main shaft then I suspect that the ball bearing was omitted.

So could be a case of replacing the ball bearing and sliding he gear back over? Is it accessible from the front of the gearbox or wild it be a gearbox out job?

Thanks for the reply though, slowly but surely narrowing it down 

[Rusty's Uncle]

Just as a check you could try securely  jacking up one rear wheel and running the engine in gear with the speedo drive in just to see if it gets any drive from the gearbox.

[ChrisRLewis]

Good advice from Rusty.
If there is no drive from the speedo drive output it maybe worth investing in an endoscope inspection camera, cheap ones are available on ebay for laptops http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR5.TRC1.A0.H0.TRS0&_nkw=usb%2Bendoscope&_sacat=0

[Geemccaw]

Just as a check you could try securely  jacking up one rear wheel and running the engine in gear with the speedo drive in just to see if it gets any drive from the gearbox.

Running the car in gear while up on the ramps does not turn the speedo drive.

 

Good advice from Rusty.
If there is no drive from the speedo drive output it maybe worth investing in an endoscope inspection camera, cheap ones are available on ebay for laptops http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR5.TRC1.A0.H0.TRS0&_nkw=usb%2Bendoscope&_sacat=0

That's not a bad idea! I'm guessing I will need the gearbox open to fix the issue though so may just have to bite the bullet and open it up. Os it aces me from opening just one end or do you think I will need to drop the whole box?

[Rusty's Uncle]

I have just assembled a gearbox from a pile of bits and it occurred to me that a further test would be to see if you can grip the speedo drive output and see if it turns. Have you driven this car and was the gearbox otherwise ok?

[Geemccaw]

I have just assembled a gearbox from a pile of bits and it occurred to me that a further test would be to see if you can grip the speedo drive output and see if it turns. Have you driven this car and was the gearbox otherwise ok?

Car runs and drives fine! I have tried two different speedo drives and both spin freely and work as they should while off the car. Just no drive from the gearbox when they are on