Speedometer Ratios on Four Speed Gearboxes

This thread is for discussing technical topics.

Moderators: Ian Grace, Will Grace

Post Reply
Sam Christie
Posts: 186
Joined: Mon Nov 20, 2006 10:37 am

Speedometer Ratios on Four Speed Gearboxes

Post by Sam Christie »

It seems most common for '74' Minor four speed gearboxes to be marked with a 4/17 speedometer ratio but some are marked 3/12. I assume 4/17 is Morris Minor. Is 3/12 associated with the Family Eight?

Image

Are any other speedometer ratios seen on '74' gearboxes ?
Trevor Wilkinson
Posts: 161
Joined: Sat Dec 02, 2006 4:44 pm
Location: Bedfordshire UK

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Trevor Wilkinson »

That has just triggered my memory, the 4spd Hornet box in my Minor has 3/12 ratio.
Trevor.
Sam Christie
Posts: 186
Joined: Mon Nov 20, 2006 10:37 am

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Sam Christie »

The difference between 3/12 and 4/17 viewed simply as fractions does not seem very significant. Is it possible a change in wheel size might have been a factor?
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Ian Grace »

My 1933 season McEvoy has 3/12, and this must have been standard for the season. So is it that the 4-speed boxes were 3/12 and the 3-speed boxes were 4/17?

But then I guess I should have learned by now that life is never that simple.
Simon
Posts: 275
Joined: Sat Dec 09, 2006 4:56 pm
Location: Surrey UK

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Simon »

Could it be that 33 Minors had 19 inch wheels and 34 Minors had 18 inch wheels.
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Ian Grace »

That is exactly correct.
Sam Christie
Posts: 186
Joined: Mon Nov 20, 2006 10:37 am

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Sam Christie »

I assume three speeds are 4/17 (is this marked somewhere?) but as you can see four speeds vary. Right hand example is a synchromesh version. I think the one on the left might be yours Ian (I cannot recall where I found the image).Could it be that the non synchromesh four speed was considered more 'sporty' for the McEvoy ? I have never experienced the synchromesh version but I think it is said to be a bit slower in changing gear. Has anyone experience of both?

Image
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Ian Grace »

Sam,

The syncro box was only available on the Minor for the 1934 season, and that's why my '33 season McEvoy has the 4-speed crash box.

It does look like my box, but I'm in the office and the box is in the garage. I'l check tonight.
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: Speedometer Ratios on Four Speed Gearboxes

Post by Ian Grace »

Yup - that's my gearbox.
Post Reply