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Speedo drive O rings? - Gearchange/Gearbox/Clutch - The Lotus Forums Jump to content
Andyww

Speedo drive O rings?

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I was just putting my speedo drive back in after removing/replacing the gearbox rear section and noticed something.

 

There seems to be some grooves which look like they should have O-rings in, but they dont.

 

There is a groove on the end of the inner nylon bush, and two grooves on the gear shaft.

 

The parts list list one O-ring which I assume goes on the nylon bush but are there supposed to be O-rings on the gear shaft?

post-16906-0-66752700-1423508411.jpg

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I replaced the O ring on mine last week and it still leaks!

 

I think it was Harry who siad he thought it was because its backwards in the Esprit?

 

Buddsy

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I was slightly puzzled by that as I thought the SM engine rotated 'backwards' so the box actually runs in the same direction in an esprit or an SM 

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If the engine runs backwards then the box must be running backwards. In the SM the drivetrain is pointing the other way so the car still moves forwards although the engine and box are running in the opposite direction to the Esprit.

 

Hence the need for the right angle speedo drive, to reverse the direction of the speedo cable.

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I yhink Orings on the drive shaft would be a bit restrictive. Wouldn't allow proper roatation at low speeds.

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I yhink Orings on the drive shaft would be a bit restrictive. Wouldn't allow proper roatation at low speeds.

 

Yes thinking about it, this isnt really a suitable place to fit O rings, if they wanted a seal there it would need to be a proper oil seal.

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I have taken my drive unit out again as oil seems to be pissing out. Well maybe that's an exaggeration but is leaking a fair bit.

 

I changed the two O rings a couple of months ago. The larger O ring is a stupid farty thin wall section something approx 22mm I.D. but only 1.5 thick. This is a real non standard size. Last time I used something like a 6mm x2.5 and stretched it on causing the thickness to reduce. It looked about right when I put it on but was expecting that to look damaged when I removed it but actually it looks ok. I tried that part back into the hole in the gear box (upside down so I could feel the fit) it felt pretty good. 

 

The smaller O ring looks ok too.

 

Looking at the drive it almost look like oils been coming up through the unit and out of the other end where you screw on the cable. I have tried blowing through the unit but it seems sealed. Unless different when running? I did only tighten the knurled nut on the cable by hand. I am wondering if the face of that cable nut seals that too?

 

I am thinking about opening the groove in the plastic part to fit a standard O ring. Looks to be space for a bigger ring.

 

Buddsy

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What I ended up doing was wrapping teflon plumbers tape around the brass part and pushing it into the nylon part, then teflon tape around the nylon part to make it a very tight fit into the casing, and pushed it in tight. I didnt bother with the O-ring at all in the end as the first time I fitted it, it simply got chewed up when pushing it in.

 

I would be interested to know if you have the same problem I have, whereby the inner unit can be removed and replaced without removing the rear cover bolt which is supposed to lock it. I never got to the bottom of this, one of lifes great mysteries.

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I would be interested to know if you have the same problem I have, whereby the inner unit can be removed and replaced without removing the rear cover bolt which is supposed to lock it. I never got to the bottom of this, one of lifes great mysteries.

 

No way will mine come out. I think they are a really weird size bolt M9 which are almost impossible to get hold of. Has yours been helicoil and changed for a M8 possibly?

 

Buddsy

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No, its 14mm across flats so M9.

 

It will forever remain a mystery :)

 

The nylon part is retained but not the brass part.

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I've seen the brass shaft of the drive wear quite badly from 'fretting' if the O ring is not present or failed.   I would guess that wear on the land below the 'groove' is allowing it to pull out without interference. - having said that, yours looks fine in the photo         

Edited by 910Esprit

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Well I fitted a bigger standard O ring in the section above the original. I was going to just make that groove bigger but as there was space I decided to add a new one. I have also kept the old one in...to be sure to be sure....belt and braces...

 

IMG_8708_zpstszqlmhn.jpg

 

I will see how we fare together.

 

Buddsy

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