Smiths Speedometer problems...

[h_m_cumming]

Re: Smiths Speedometer problems...

Well that's one I haven't seen before. When I rebuilt my 5sp. Fiat box I don't recall a dedicated breather, there was enough clearence round the gearlever area to allow for heat pressure expansion and contraction. Only other reason might be if the oil level is too high. Normally speedo cables tend to run dry and need lubricating.??????

[element]

Re: Smiths Speedometer problems...

Yes exactly! However, the cable entry point is at the bottom of the gearbox if I recall right; even if there were too much oil in the box - what gives it the drive to come up the cable? Besides - I think the hole was small where the drive pin went in and there'd not be a lot of room for oil to escape let alone come up the inside of the cable - uphill by about a metre!

[element]

Re: Smiths Speedometer problems...

I've just been told it's likely to be the seal on the speedo drive of the gearbox that has failed. I doubt they are easily found these days to enable repair. I'll have to find a way of just sealing it off when I change the speedo for a different, programable one.

[Kahawi]

Re: Smiths Speedometer problems...

This may not be relevant, but I think we can assume your gearbox breather has an issue, forcing oil up the cable.

The speedo works by a rotating pair of magnets, inducing ‘eddy currents’ into an aluminium flanged disc, which allowed to rotate and is attached to the pointer.

The disc is retarded by a coil spring, it always wants to return to the end stop, but the faster the magnets spin, the more it has to rotate about the dial. A little bit like the old-fashioned domestic electric recording meter.

The gearbox oil has almost certainly got into the very small gap between the rotating magnets and the (sort of) fixed ally disc, however your dial still looks quite clean, as do the mileometer discs.
I would be inclined - if you can remove the chrome escutcheon - to lower the mechanism, level and face up, into a bowl of solvent – white spirit – ‘Gunk’ Meths etc. only until the rotating mechanism is under water and see if you can flush out the oil.

You may also need to remove any ‘filings’ off of the magnets. But these units were quite strip-down-and-repairable if you are careful. Making sure that you mark the alloy disk with some reference to 0mph or see if there is an end-stop to get the pointer back in the right place when done, it is usually a push-fit onto the tapered shaft.

You might get some idea of speedometer innards from these pictures:-

http://www.kahawi.co.uk/hourmeter.html

[h_m_cumming]

Re: Smiths Speedometer problems...

If you can get the old seal out there will be a number on it . Should be available on line. Or even quote dimensions. Is it in the drive or in the box?

[h_m_cumming]

Re: Smiths Speedometer problems...

Further think on it; the seal must be in the angled drive itself because the drive casting goes right in to locate the gearbox gear and the drive gear.

[meverett]

Re: Smiths Speedometer problems...

I have the Marina 4 speed gearbox and the seal is on the drive unit in the side of the gearbox extension. I think it is likely that if the seal has failed then the oil can ride up the cable in a screw type motion.
Remove the cable and place upright to see if oil drains back down. The seals for the drive unit must still be available.

[meverett]

Re: Smiths Speedometer problems...

I fitted an electronic speedo from CAI some while ago. At the time of ordering I requested in writing that the mileometer was set at the current mileage so the mileage history was preserved for all the documentation (MOT / Insurance etc). Mine also has a sensor that picks up from the diff flange. The diff bolts are not equispaced on my Siera diff so I used split tubes pressed into the other redundant equispaced holes in the diff flange so they protrude at the back of the flange. There is a post somewhere on the forum with photos. Peter.

Hi Peter,
I have the electronic Smiths gauges TES3 speedo and TET3 tacho. I am in the middle of rewiring the whole car. Do you have any documentation on calibration and sensor pickup fitting that would help me when the time comes. I have some fitting instructions for the TES5 series that I downloaded but nothing for TES3 or for the sensor fitting.
Cheers, Martin.

[element]

Re: Smiths Speedometer problems...

I can't find the speedo drive replacement seal as such.. but I have found this:

http://www.ricambio.co.uk/69-fiat/71-131-132-argenta/456-clutch-and-transmission-parts/gearbox-speedo-drive-fiat-124-131-lancia-beta

I believe it might fit the Fiat Gearbox in the car.. Instead of trying to find a component of the speedo drive - just replace the speedo drive...? I'll maybe give them a ring and ask.. However, I don't know how easy it will be to remove / replace the speedo drive unit on the gearbox - or whether I need to have the gearbox out to do so because of the surrounding construction. I would then have to look at stripping down and cleaning / resetting the speedo itself - or getting it repaired, if it can be..

I have also found this:

https://www.ebay.co.uk/itm/85mm-GPS-Speedometer-Gauge-140MPH-Chrome-Bezel-Stainless-Waterproof-f-Car-Truck/112579087966?hash=item1a363c8e5e:g:bkwAAOSwwGdZyyJ9

Which would be significantly simpler to fit - all I'd need to do then is blank off the speedo cable point on the speedo drive at the gearbox which can't be too difficult.

So maybe £30 for a new speedo drive, if I'm lucky fix the speedo myself or (more likely) pay £80 & double postage for someone else to repair it - if indeed it can be repaired now its been doused in gearbox oil.. or pay £64 for a new gps speedo that will work perfectly...

Hmmm...

[meverett]

Re: Smiths Speedometer problems...

I would try to fix the speedo first then if successful strip out the drive unit and try to find seals for it, if not replace the drive unit.
If speedo completely knacked then you haven’t spent out on it and the gps sounds a good option.

[element]

Re: Smiths Speedometer problems...

Very pleased to announce that I have successfully fixed the speedometer.. I spent ages cleaning the gear oil from inside using acetone, isopropanol & methanol with a small art brush first of all the liberally dousing it and flushing it through. Then put it in the greenhouse to thoroughly dry out I removed & hung the cable vertically in the greenhouse to drip all it's oil into a jam jar beneath. Then pulled the inner cable out and ran it through a dry cloth.
Finally refitted the cable and gauge and drove 100m.. perfect. Now have the awkward job to remove the speedo drive from the gearbox under the car..
That's for tomorrow evening..

[Kahawi]

Re: Smiths Speedometer problems...

It would be ‘interesting’ to know if the flexible inner cable is laid clock-or-anti-clockwise? One way, would feed oil up, t’other would tend to pump it back down the outer, (depending on the rotation). OK it’s a minimal amount, but over time..?

I wonder if the Swansea repairers sent you a cable that was wrong-handed?

Good to know that you fixed the instrument yourself, isn’t that a great feeling when you’ve saved a bucket-load of money!

Good luck locating an oil seal.

Best regards,
Colin B

[meverett]

Re: Smiths Speedometer problems...

Nice one sorting out the speedo. Good luck with the drive gear and hope it’s also a success.
As above comment, if your cable is stripped out try plugging it into the drive gear and by rolling the car forward will tell you which way it rotates and give you an idea if oil is being forced up the cable.

[element]

Re: Smiths Speedometer problems...

Tonight I jacked up the car and supported it high enough to get in at the speedo drive... one single allen key bolt.. hmmm that looks easy enough... 6mm bolt removed and then sliding the speedo drive out (sideways) of the gearbox all was going swimmingly until it bumps against the propshaft tunnel.. It can't be removed without a) removing the gearbox from the car or b) cutting a hole in the tunnel behind the floor carpet.
a) necessitates the engine & gearbox removed and b) necessitates the whole interior, seats and carpet before cutting a hole... I don't fancy either job.
So I'm now stuck with a speedometer that works but if I use it - it will get refilled with gearbox oil after a (?) while... Looks like I'll have to buy that GPS one on eBay from China for £62 - which will require a bigger hole in the dashboard by 5mm all around the edge of the current speedometer hole.. I'll also have to figure a way of stopping the speedo drive pushing oil out... I think I'll try to get a stop end cap with an inner thread that matches the sleeve nut that tightens up around the cable at the speedo drive.

So I can maybe sell the current speedometer to pay towards the new GPS one... or just refit it and use it until the new one arrives. It may have taken anything from 1 to 1500 miles of running for the oil to reach the speedometer as that is the distance since fitting it last May.

The thought about the speedo cable running either clockwise or anticlockwise has me thinking a little... From looking at it; both ends appear identical and the inner steel rod cable is square ended at either end... So in theory, I could turn the cable around and fit it backwards. The more I think about this idea the more I see it will probably be fruitless because it will still turn the same way - the turning motion is governed by the gearbox speedo drive not the cable itself.

[meverett]

Re: Smiths Speedometer problems...

You got me thinking now, you are right with the cable as if it is shaped like a screw thread then either way round the thread will be the same. (Had to draw a picture to prove it to myself).
Is the speedo drive mounted towards the top or bottom of the gearbox. If it’s at the bottom you may be able to remove the prop shaft and gearbox mount then lower it on a jack or push sideways slightly, would that give room to remove the drive. Seems a shame to give up now as you have had success on the speedo itself.