Morris Minor Owners Club

Hi Guys,

Whilst rebuilding and modifying my '56 Series II, I've discoverd that it has been fitted with a 1376 TPM ratio speedo. Not only that, but it had a 948 engine and the standard 803 type gearbox. I don't know what the diff ratio was, as I haven't mananged to remove the rear axle.

Does this seem to be an odd combination to anyone else? It seems to be quite a jumble of parts to me.

Cheers

John

Hi John
I have a 1376 TPI speedo, with a 4.22 diff and a 803 box, which is fitted with a 2.6 cable drive in the gearbox, instead of the standard 4.4.this reads about 5% fast, near enough for me. If your speedo cable drive pinion in the gearbox has 13 teeth, its a 2.6, if not you may have to change it, and thats a gearbox out job, but of course you need to know your diff ratio, before you go anywhere. Hope that helps.
Win

The normal speedo for a late Series 11 is serial No 511440109, TPM = 1000. If you have a 948 engine and you are revving the nuts off it in top gear then you probably still have an 803 diff.

I wasn't aware it was possible to change the speedo cable drive ratio? Is this on an A series box ??

The speedo / pinion ratio is given as 5/13 for the 948 box, 6/17 for the 848 Mini and 6/15 and 6/14 for the 1500 and 1750 Maxis.
All totally useless information except to show that speedo drive ratios can change. There is not enough published information on Minors to make any comparison but I would guess that the SMM and S11 have different drive ratios to the 948, 1098 and 1275 as the speedo TPMs of 1600 and 1000 do not fit the same pattern as the latter speedos

There are various speedo drive ratios for the Mini - but they won't fit the Minor box.......... I've never heard of any diffrent ratios for the Minor box.

I had calculated that for a Toyota 5-spd with 3.5:1 speedo drive ratio, 3.9 diff and 165x13 tyres (now 185/70x13), I would need a speedo with ~990 tpm, and I came across the Series II 1000 tpm speedo at Mr Grumpy's Minors in Oxford during the restoration in the 90's, which was exactly what I was looking for! Couldn't believe it, as I didn't know that the in-line A-Series gearbox had ever had a different speedo drive ratio?

The 803 box speedo worm wheel on main shaft is a 2 start and the gear has 9 teeth = 4.5 to 1.
The later box speedo worm wheel on main shaft is a 5 start and the gear has 13 teeth = 2.6 to 1.
I have changed these on my boxes, to use the 1376 speedo head.
Sorry on the previous post I put 4.4 instead of 4.5 for the 803 box.

Win,

Thanks for the info, when I found the speedo head I was told it was for a Series II, and it works perfectly, and now I know why!!

Well well well! Never knew that - learn something new every day - thanks for the info Win - although I can't see me using it myself.

If the speedos all had the same ratio pinions then the Series MM would have a TPM of 1504 since it has a 4.55 diff and the Series 11 would have a TPM of about 1700

Well - the MM was a very different gearbox of course!