Broken Speedo
Author
Discussion

Noblescort

Original Poster:

198 posts

229 months

Monday 23rd March 2009
quotequote all
My speedo has stopped working. I've searched the threads to see if there is any info that might help but the only info I can find suggests electrical problems in connectors somewhere along the loom. I have checked the wiring and this is all OK, the problem is that the square drive that goes into the top of the gearbox has sheared. The plasic sender unit is clipped onto a plastic base that threads onto a steel boss on the gearbox. The square drive pin has sheared somewhere inside this boss. The boss seems to be retained into the casing by a roll-pin. Can anyone tell me how to get this out so that I can replace it?

AMG Merc

11,955 posts

282 months

Monday 23rd March 2009
quotequote all
Search come more. You should find lots on the likely problem - the sensor inside your offside front wheel.

Adrian W

15,493 posts

257 months

Monday 23rd March 2009
quotequote all
AMG Merc said:
Search come more. You should find lots on the likely problem - the sensor inside your offside front wheel.
Am I missing something or do you need to read his post again?

AMG Merc

11,955 posts

282 months

Monday 23rd March 2009
quotequote all
Adrian W said:
AMG Merc said:
Search come more. You should find lots on the likely problem - the sensor inside your offside front wheel.
Am I missing something or do you need to read his post again?
I need to read his post again.

F.C.

3,901 posts

237 months

Monday 23rd March 2009
quotequote all
I could be barking up the wrong tree here but if you haven't (i'm guessing not) got access to the opposite end of the roll pin to tap it out with a pin punch, you could try a small self tapping screw (it will need to be hard, stainless??) into the end and once it has bitten lever it out that way.
You need to be careful as the roll pin will expand if you go too far and you could damage the housing.
You could also try a small easy out (used to extract sheared screws and bolts)but again it will tend to expand the pin as it bites.
No doubt someone will suggest a roll pin remover (do they exist?)
F.C.


Noblescort

Original Poster:

198 posts

229 months

Monday 23rd March 2009
quotequote all
AMG Merc said:
Search come more. You should find lots on the likely problem - the sensor inside your offside front wheel.
You must be talking about newer 3, 3R or M400 cars, mine is a 2.5 litre and the sender is definately in the gearbox casing.

F.C. said:
I could be barking up the wrong tree here but if you haven't (i'm guessing not) got access to the opposite end of the roll pin to tap it out with a pin punch, you could try a small self tapping screw (it will need to be hard, stainless??) into the end and once it has bitten lever it out that way.
You need to be careful as the roll pin will expand if you go too far and you could damage the housing.
You could also try a small easy out (used to extract sheared screws and bolts)but again it will tend to expand the pin as it bites.
No doubt someone will suggest a roll pin remover (do they exist?)
F.C.

I thought about these methods but I am concerned with

a) expanding the pin when the screw is inserted thus increasing the force holding it in
b) damaging the end of the rollpin

The roll pin does project a few mm so I also thought about Mole-Grips on this end then tap the Moleys. I also thought about drilling out the roll-pin which concerned me just as much.

None of these methods feels particularly good, I thought I might be missing a trick, hence the posting on here!!!

What I really need is feedback from someone who has actually removed the boss from the housing.

But keep the ideas coming!

Noblescort

Original Poster:

198 posts

229 months

Thursday 2nd April 2009
quotequote all
Finally got the speedo drive gear out!

In case it helps anyone else, this is what I did.

Welded a bit of M5 studding to the end of the roll pin. Slid a bit of tube over the studding so that it bears on the casing. Put a couple of thick washers on the end of the studding, then wound a nut on and hey presto out it came.

This is what I found when I removed the drive gear



It's supposed to look like this



Anyone got any idea how this might have happened?


daddysumo

2,545 posts

242 months

Friday 3rd April 2009
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Ok Im lost. The speedo runs from a transducer on the front hub on my car as on all the others I thought ?
If this is so why are you concerned with the drive on the gearbox which isnt used ?

Steve

Noblescort

Original Poster:

198 posts

229 months

Friday 3rd April 2009
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You must have a newer car than me!

On my 2.5, the drive comes from the gearbox. The results of which you can see above!

CTO3

334 posts

236 months

Friday 3rd April 2009
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hi steve

think on 2.5's the speedo feed is on the gearbox casing not the front hub as on later cars. mine is front left (M400)


conleth

daddysumo

2,545 posts

242 months

Friday 3rd April 2009
quotequote all
Ah that would be it then