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MG Midget and Sprite Technical - Type 9 23 teeth speedo drive gear

Anyone got a spare one of these they don't mind selling? I stripped the teeth on mine when I put the speedo cable outside of the square hole instead of inside.
I've done some calcs and need a 23 teeth gear with a speedo with 1060 TPM. I've got the speedo, just need the gear.
No-one seems to have any stock and I'm reluctant to pay £55 for one off ebay.
Rob
MG Moneypit

Rob

Guess you have tried asking BGH Geartech http://www.bghgeartech.co.uk/html/bgh_home.html or Burton Power, or these folk: https://www.bearingkits.co.uk/TYPE-9-GEARBOX-SPEEDO-DRIVE-GEAR-23-TEETH/592.htm

Cheers
Mike
M Wood

Burton power used to sell the 22 tooth gear but NLA. I've searched their website but cannot find any available at all.

Bearingkits have them but £42 + post.

BGHgeartech I'll have to ring them as I can't see any on their website.

www.type9gearbox.co.uk have second hand ones on their website but when you try to buy one it says "This store is not yet accepting payments.
Please check back later", whatever that means.
I'd have one of these but there are no contact details at all.

The ones on ebay at the moment have 3 different sellers but exactly the same price (down to the penny) so I think they are the same company.

I'd rather have a second hand one just at the mo.

Rob
MG Moneypit

Rob, I have several but don't think I have a white one and believe they are colour coded for the number of teeth. But I will check.
GuyW

Hi Guy, I think Ford original are colour coded but others manufacture them and don't stick to the colour code.
Let me know what you have got. I can re-calculate and maybe use a different Speedo.
Rob
MG Moneypit

This might be useful.

The original Ford speedo drives (pinion) came in various colours.

22 teeth: Brown, yellow, and white.
23 teeth: Black.
24 teeth: Green, and grey.

The WORM drive in the tailshaft, is either 7, or 8 'teeth'. (really spirals).

The ribcase original speedo drive is 2.6:1 (13/5).

The T9 box has a number of different speedo drive ratios.

With the speedo worm drive gear in the Type 9 gear box being either 7 or 8, and the driven wheel (pinion) either of 22,23,24; then the closest you can get to the original ribcase of 2.6:1. is 22/8=2.75:1.

So if you have an original FORD coloured drive(pinion), that's an 8 worm in the tailshaft, and a Brown, Yellow, or White pinion.

And it depends on what your T9 came out of, as to whether you have a 7 or 8 worm drive.

A 2 litre OHC had both 7 and an 8 worm.
A 1.6 litre ohc had and an 8 worm.
A 2 litre V6 had and an 8 worm.
A 2.3 litre V6 also had and an 8 worm.

Then it further depends on the diff and tyre sizes of course, as to what your speedo needs.









anamnesis

The way I worked it out is TPM from speedo x 2.6 gives propshaft TPM divided by diff ratio = wheel TPM.

So for standard Frogeye you get
1472 x 2.6 / 4.22 = 907 wheel TPM

So working backwards for a Frogeye with 3.9 diff
907 x 3.9 / 2.6 = 1360 so you need a speedo marked 1360 to display correctly but 1376 is available but not with a frogeye dialface.

I've got a Frogeye with 1330 engine and Type 9 gearbox with standard tyres. If I have a 23 tooth gear with 7 spiral in the gearbox it gives a ratio of 3.29 so the speedo I need is
907 x 3.9 /3.29 = 1075 TPM.

The nearest is from an MGB SN6125.04 which has a TPM of 1060. Of course the dialface is nothing like a Frogeye but I think it could be made to look similar (apart from the 120mph maximum).

Rob
MG Moneypit

Rob, no luck I am afraid. I am struggling to find them. I did find a black one, but that has 24 teeth. Not as Anam's list although I believe this is an original Ford one. I only ever collected them from scrapyard road cars which would be unlikely to have been changed for an aftermarket one. I know I also have a green and a brown one - it's just that they haven't shown themselves yet.

You calculation method is a bit complicated! Probably mathematically correct I know. When I set mine up I just drove it with the original pinion and compared the speedometer reading with a GPS App on my phone. Noted the percentage error on the speedometer and choce an appropriate pinion to correct by that percentage. That's why I have the selection of pinions - so I could swap around to get the best match to my GPS figure. I cannot now remember which one I ended up with!
GuyW

Ford's list Guy, from a Ford T9 workshop manual.

It's quite possible Ford changed the colours when they introduced tbe 5 speed. The pinion also fits the type E 4 speed box, which Burton list black as 24 teeth too and they've been going since 1963. So yours could possibly have been from a rebuilt box using a burton part or a 4 speed part.

None of which helps. 😶

For extra cost, the speedometer can be calibrated for the exact tpm by richfield and speedy cables, but the mileometer would have to be to the nearest gears available. But it wouldn't matter much if thr miles count was off a tad would it?



anamnesis

There was a time, which doesn't feel so long ago but must have been mid '90s, when the local scrapyard was full of old Sierras and ford pckups with type 9 boxes. The local yard was only interested in heavy metal items for weighing in. Most other stuff was either very cheap or free for plastic stuff, body trim switches etc as long as you stripped it down yourself. I knew the owner anyway and always showed him what I was taking. I also helped out at times unloading vehicles and removing batteries and fluids as they came in, so I guess it balanced out anyway.
GuyW

You're so right Guy. The mid 90's doesn't feel so long ago. It seems the older I get, my past feels closer. Very odd.
anamnesis

The gears are available here

www.motomobil.com/products/schaltgetriebe-tachoritzel-5-gang-typ-9-23-zaehne-60110590-9

You need to be careful in choosing, because there are different variants (not just the number of teeth).

Some have a square recess for an RPM sensor, others do not. You can only tell which one to get when you have the old one in your hand. my five speed had the RPM sensor, but I was able to fit the other the by replacing the sensor with the metal cap.

While you are at the job, it is also a good idea to replace the oil seal (www.motomobil.com/products/schaltgetriebe-tachoritzel-simmering-5-gang-typ-9-15798600-15) as this often leaks and can only be replaced when the gear is out.

Just realised the site has an English option too, but I'm being too lazy to redo the links.....
Dominic Clancy

Thanks for all the feedback, most welcome.
I've just found that an SN6125/06 has a TPM of 1040 so if I use a 24 teeth speedo gear I can get a TPM of 1035 at the speedo cable. This is so close any error will be miniscule.
The reason I want to use an SN6125 is because, and not everyone knows this, the trip meter has digits close together whereas others (like the SN6144) has spaced out digits (only on the trip mileage) with dividers on the face plate between each digit. The indicator finger is also almost identical on the sn6125 and Frogete speedos.
The close trip digits also feature on the Frogeye speedometer so I should be able to print a convincing centre disc and apply it to the centre of the MGB speedo. The only giveaway would be the 120 mph max speed and the text below the little jeweled light which I will have to change from Blue to Red.
So I have a choice of 23 or 24 teeth. Anyone got a spare 24 teeth speedo gear?
Rob
MG Moneypit

R ob, yes I do. See my earlier posts in this thread. Anam suggests mine may not be an original ford one as its black, but its definitely got 24 teeth. I now gather also that there are two types. PM me and I can send some close up photos to check it's what you need. Or I could just post it for you to try.
GuyW

Great Guy. I've sent you a message via FB, assuming you live in Kendal I've messaged the correct one!
Rob
MG Moneypit

I will check that later Rob. I don't get fb stuff on my phone. (Compartmentalizing!)
GuyW

This thread was discussed between 16/09/2021 and 21/09/2021

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