Various speedo questions

[purps]

Hello all, I have some speedo questions please. Read a few bits on this forum already, but having trouble piecing it all together. Allow me to set the scene...

- 1960 minor 1000 saloon with original speedo (I believe, how do I check?)
- fitted with 1098 cc traveller engine with its gearbox (I believe, how do I check? Gearbox is ribbed type if that helps)
- needle appears to indicate a higher speed than reality (I have not measured this, but fairly sure I wasn't doing 80 mph the other day )
- needle jumps around quite a lot generally
- approximately 1 in 10 journeys, there is *click* that comes from the dash. It is regular, its frequency is about once a second, and the needles jumps up perfectly in time with the click.
- piccie of speedo attached.

So here come the questions...

- Assuming I am correct about what's what, does it matter that I have a saloon speedo coupled with a traveller gearbox? The odometer is pretty accurate (I checked with GPS), but is the speedo reading too high because the gearbox is wrong? How can the speedo be wrong and the odometer be right?

- Is the general jumping around and also the clicking issues due to the cable not being oiled? Am I right in saying you can have too much in oil in the cable? Or could it be an issue with the speedo itself?

Cheers,
Matt.[frame][/frame]

[bmcecosse]

The speedo depends on the final drive ratio - not the gearbox (except early 803 pudding stirrer gearbox) and for a 1098 engine the car should have a 4.22 final drive and would have a 1408 tpm speedo. Yours is 1376 - so not too far wrong (and you say he odometer is pretty accurate) - and anyway you don't know the final drive ratio - or do you? The speedo needle is not sitting at zero - so it's possible the spring has been stretched. Jumping is associated with the cable sticking - or not connected properly at the speedo. I would pull the speedo and investigate why it's not at zero - and pull the inner cable out and give it a wipe with Moly grease - but not the last 12" at the speedo end.....and refit it after adjusting the needle down to zero.

[chesney]

Someone has retrofitted your '60 with the speedometer and gearbox of a later car, probably a 62/3/4 model. As standards it would have had a 1504/1525 speedo that would read to 80mph, a 4.55 diff and a smoothcase gearbox and 948 engine.
Check to see if the diff has a filler plug on the diff casing itself, on the right hand side looking from the back of the car iirc.

[purps]

Sorry for the late reply, took me a little while to digest that.

OK sounds like I need to have a look at the speedo. The speedo cable is also missing some of the outer plastic, so maybe oil is leaking out as well?

I can't quite wrap my head around why the diff matters to the speedo? The cable attaches to the gearbox, so why does it matter? Sorry if that's a dense question.

Cheers,
Matt.

[chesney]

The final drive ratio affects the speed per revs, all gearbox speedo drives turn the same TPM (turns per mile) but the final drive, as standard on your car, would take 4.55 revs from the prop shaft to turn the wheels a complete turn (in 4th/direct gear). The diff fitted in your car has a different final drive ratio, 4.22, and will take 4.22 prop shaft revs to turn the wheels once. The speedo makes up for this, a 4.55 diff needs a 1504 TPM speedo to read accurately, a 4.22 diff needs a 1376 TPM speedo, as you have.

[bmcecosse]

Later cars have 1408 tpm speedo with the 4.22 final drive.

[chesney]

I'm not all that sure they do BMC, for sure the black speedo fitted to my '68 is a 1376 and the 90 MPH bronze speedo fitted to my '61 (retrofitted to my car from a '63 model) is also a 1376, as pictured above. Both have a 4.22 diff.

[bmcecosse]

My 65 Trav certainly had the 1408, and there are plenty about. They perhaps realised they were stretching the 'optimism' of the speedo readings a bit too far and changed to the 1408 at some point. The difference of course is hardly significant.

[chesney]

Is this the traveller with a 3.7 diff fitted? ;)

[bmcecosse]

It NOW has a 3.7 final drive - and a 1249 tpm speedo which is absolutely accurate on speed and miles (155 tyres on 4.5J wheels).

[chesney]

Ah, just checking ;)
I suspect you're right BMC, just because I haven't seen it doesn't mean that 1408TPM speedo's don't exist.
The plot thickens, as there are two types of 'black face' speedo, ones with a circular pattern, and ones with KPH figures. May have to look deeper into this.
BTW, my 1376TPM speedo is spot on all the way up to 70MPH (plus more I assume should the law of the land allow ;)) with 185/65 tyres fitted. Bit I suspect it was never reading right from having 5.20/14's from the factory!
Interesting to know your current speedo configuration BMC, I have a 3.9 in stock somewhere to fit so I can work from your TPM figures...

[bmcecosse]

It's just fortunate that there is a Mini speedo with 1249 tpm.

[mike.perry]

There is a chart showing speedo aplications on http://seriesmm.mmoc.org.uk Car Ident, speedometers. Speedos of that period nomally over read so a 1408 tpm, the 4 figs after the serial number, will read fast on a 4.22 diff but experience has shown that it is almost exact when used with a 3.9 diff.
The 948, 1098 and 1275 gear boxes have the same pinion to drive gear ratios so the box will make no difference to the speedo reading. The 918 and 803 boxes have different ratios so speedos cannot simply be swapped over

[purps]

Thanks for the information gents, I see how the final drive is important!

My speedo has since got stuck on 1,499.9 and the clicking I mentioned in my first post is now continuous. I've pulled the speedo and gone for a little drive, and I cannot stop the cable from turning with my fingers so I assume everything from there back to the gearbox is OK.

This, combined with the erroneous speed reading, makes me think it's time for a new speedo! However I will pull it apart in case there's something obvious jamming it up. I also need to check what my final drive ratio is, I don't know if I have the original 1960 diff, or the later diff that matches up to my 1098 engine.

Cheers,
Matt.

[don58van]

Hi Matt

There are tiny gears built into the wheels of the odometer that push the next higher wheel around when it gets to 9.

That means that there is extra friction on the speedo drive when it gets to 9. When there are two wheels on 9 the drag gets much higher. When three get to 9 it is higher still...

The clicking noise you hear is the ratchet drive for the odometer 'trying' to turn the wheels, but failing to because there is too much friction. This friction affects the speed reading in a rhythmic fashion each time the pawl unsuccessfully pulls at a tooth of the cogwheel.

When speedos fail, they usually display xxx999 or similar.

The only solution is to disassemble the whole thing and clean and (where appropriate) lubricate it with proper instrument oil.

The servicing of the odometer is quite tricky, so only for those very adept at this type of thing.

OR - replace it with a good speedo.

Good luck with sorting it.

Don

[jonjeans]

Hullo all. Regarding Bronze faced Speedos on ’57 car. Mine is duff in so far that the speedo works, but odometer has failed. This is the indicator in speedo version, 2 x Orange warning lights at top, red charge, orange oil at bottom.
Any one have one for sale please? Preferably working 

Many Thanks

[mike.perry]

You need to know the TPM, in your case if it is a standard 948 Minor then it should be 1504

[bmcecosse]

Or just free off the odometer.....

[jonjeans]

Than you for the input.

I suspect Odometer is “kaput” and am reluctant to investigate and lose a working speedo.

Speedo detail: SN4401/15 1500

Should anyone have one they wish to sell I would welcome the opportunity to buy.