What is the RIGHT speedometer

[SriVik]

Can anybody tellme what is the RIGHT speedometer for 1963 saloon 1098cc 4.55 diff ???
I need SN and TPM number if can ..

Better if the owners of such models can help me..

[Sleeper]

Here you are...

http://potteries.mmoc.org.uk/ID/Speedo.htm

John ;-)

[ManyMinors]

Hard to say what is the "right" speedometer for a car which has a 1098cc engine and the diff from a 948cc car. It'll depend on what tyres are fitted to an extent. I would stick with the correct speedo for the diff using the table provided, and then check for accuracy with a satnav.

[SriVik]

This one doesnt have mine..

Here you are...

http://potteries.mmoc.org.uk/ID/Speedo.htm

John ;-)

[SriVik]

i got this info from morris factory, it was built such ways..
apparently some 1098cc comes with 4.55 as optional...

Hard to say what is the "right" speedometer for a car which has a 1098cc engine and the diff from a 948cc car. It'll depend on what tyres are fitted to an extent. I would stick with the correct speedo for the diff using the table provided, and than check for accuracy with a satnav.

[philthehill]

The nearest you are going to get to the correct speedo is to look for your chassis number on the Potteries list against a 4.55 diff.

If it is not listed all you can do is pick a suitable speedo for a 4.55 diff.

The speedo drive worm gear on the main-shaft and its matching pinion are the same part number for both 948cc and 1098cc gearboxes.

i.e. 2A3420 & 2A3371.

So the speedo cable entering the back of the speedo will be rotating at the same rpm whether it be a 4.55 or 4.22 diff.

Unfortunately once you go from original factory specification (re 4.22 diff) to an optional extra diff (re 4.55 diff) it all becomes rather difficult to determine the correct ex factory/optional diff speedo.

What speedo do you have currently fitted? Is there a problem with it?

[Sleeper]

" So the speedo cable entering the back of the speedo will be rotating at the same rpm whether it be a 4.55 or 4.22 diff. "

For the same road speed?

John ;-)

[philthehill]

Correct.

[Sleeper]

Sorry Phil , I respect you , but , how can it ?
If the wheel/tyre sizes are the same , for a given road speed the gearbox output shaft ( and prop ) , will be spinning at different rpm's for different diffs?

Surely...

John ;-)

[philthehill]

The gear driving the speedo cable is the same for both 4.55 and 4.22 so the speedo cable will turn at the same speed as the gearbox output 3rd motion shaft whether the gearbox is 948cc type or 1098cc type.
You are right that the diff does effect the revs of the 3rd motion shaft and that is why I said that the OP needs to select a speedo suitable for a 4.55 diff from the Potteries speedo application list.
Phil

[SriVik]

Mine is modified by previous previous owner , currently sn4419/04 1376. This fitted on the late 1098 models
(which i believe 4.22 diff).

Gearbox running at a speed where speedo corrected for Diff correction.. i got the idea..
Meaning, for 4.55 is 1504 TPM And 4.22 means 1376 TPM

[Sleeper]

You're not far off..

4.55 : 4.22 is 8%

1504 : 1376 is 9%

John ;-)

Edit.

But ideally you should start from measuring the indicated mile/speed against the actual mile/speed with a satnav ( or whatever )...

[SriVik]

Thanks for info ... good info

[philthehill]

Update:-
SriVik has posted a photo of the diff nose casing on the Morris Minor Owners web site clearly showing that that the diff casing is relative to a 4.22 diff.

https://www.morrisminorowners.co.uk/vie ... 14&t=13192

I would find it very strange that BMC would put a 4.55 crown wheel and pinion in a 4.22 carrier when the 4.55 diff assembly was available off the shelf as a complete unit with oil level/filler plug in the nose.

Hopefully having now identified the diff as 4.22 it will make identifying the correct speedo much easier.

Phil

[ManyMinors]

The 1098cc vans and pick-ups were supplied with 4.55:1 differentials weren't they. However, I cannot remember whether they came with the usual oil filler in the diff casing or not.
I hadn't heard of 1098cc cars being offered with the option of a 4.55:1 diff. but maybe they were for some overseas markets? I'm guessing that the OP isn't in the UK?

[SriVik]

We not sure what happened in 1963/64 and how the factory worked at that time.
4.55 by factory certificate, they could be mistakenly printed or could be dispatched with 4.55 then somebody changed to 4.22 previously.. or worst case the casing is 4.22 but the wheel inside is 4.55 in rare chances.

Anyways, after speaking to many, i think 4.22 is best for 1098 saloon and matching speedo.