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MG Midget and Sprite Technical - Morris Minor Gearbox

IS a ribcase gearbox from a 1098 Minor the same as that in 1275 midget?

thanks

Rob
Rob Storer

Same box, different ratios and clutch fork.
Bernie.
b higginson

Thanks
Rob Storer

Also different input shaft, and IIRC something inside is in a cheap and nasty brass bush instead of a roper one.
Max max-at-midgetmax-dot-com

Hi Max

You probably mean the first/third motion shaft bearing, or as you would say: irst/tird otion haft earing.

A
Anthony Cutler

Different mainshaft, also.
Dave O'Neill 2

In the 1098 Minor/A40 box, the 2nd and 3rd mainshaft gears have phosphor bronze bushes and in the Midget they run on needle roller bearings. Plus different mainshaft as above.

Also Minor has wider ratios, which means different first motion or primary shaft and different layshaft.
The 1275 Midget version has the same ratios and bearings plus different helix angle on the helical gears and a reverse light switch (was this on all, or just the later ones?).

The lower 1st gear Minor ratio with a 1275 Midget engine could give the half shafts a bit of a hard time?

Richard
Richard Wale

My old modsports car had a 1098 box. It went off the line like a scalded cat, but I had to rev the nadgers off it in 2nd so it didn't drop out the power band in 3rd. Surprised a few people tho ;-)

Ant - "Though" in Maxshorthand
Max max-at-midgetmax-dot-com

Had found a cheap rebuilt minor box. I thought i may be able to use this instead of rebilding me existing box.

I'll be rebuilding my box.
Rob Storer

Whilst we are on with this topic...
I have a 1098 engine that I intend using in my Frog - some time in the distant future (long rebuild!). I have a smoothcase box for it, but of unknown internal condition. I know of a 1098 Morris Minor box which I had thought of acquiring in case the smoothcase one is shot. But would it fit? Something mentioned here about different sized input shafts?

Maybe I should wait fore a Spridget ribcase to come along? I am in no hurry!

Guy
Guy Weller

Oh it fits OK, I used to run one, thrust is only thing that had to be changed. I'm not a techie, but the shaft has a different number to the 1275 one but it must be otherwise the same.

You should look for a 1275 box, I'll bet there's one for sale on a well-known internet auction site. Oh yes, there's one ;-)

Max max-at-midgetmax-dot-com

Max,
The difference is that I think the Moggie one is free!

But even as free, I don't want to take it if it won't work. I am not planning on any performance upgrades to the 1098 - this one is to be for "period motoring" ;-)
Guy Weller

Guy,

The input shafts have different numbers that relate to the gearsets in the box (minor are lower) the shaft sizes/splines are the same.

There is a bit about this in the Moss catalogue that explains the numbering system.

R.

richard boobier

the 1275 Midget box input shaft is stamped 22G229 and has 20 teeth, while the Moggy one is 22G171 and has 19 teeth.
David Smith

So will the Moggy gearbox need to match to a different clutch driven plate with 19 splines, different from the MG one?
Guy Weller

Learn something every day! I was sure the moggy gearbox would fit to a Midget without changing the clutch. I always though the differences were as above but the input shaft was the same. Just shows we never really know!
Robert (Bob) Midget Turbo

The 19 David is refering to is the number of teeth on the first motion shaft Gear End for a moggy set of ratios (not gearbox splines)

The 22g171 has 10 clutch splines and 19 gearteeth to mesh.

Moss book notes all sorts were put in even by B.L. when reconditioning.

All should fit.

R.
richard boobier

Thanks Richard, now I understand!
Guy Weller

Ahh me too
Robert (Bob) Midget Turbo

Here is a list of the pieces/parts in the Spridget/Morris gearbox. You have to download the PDF for it to be readable:
http://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/showflat/Number/407376/Searchpage/1/Main/41511/Words/transmission/Search/true/Transmission_partslist#Post407376
BillM
Bill Masquelier

Also be carefull fitting a ribcase where a smooth case has come from. Backplate thickness and clutch spacings make for some interesting combinations.

Guy, you can get a 1275 ribcase gear set into a smoothcase box with a little machining if you want to retain a little of that 'original' look...

Mark.
M T Boldry

Most of this is way too techo for me, but I have Morrie 1000 gears in my ribcase box and they seem to work just fine. I bought a set of gears (off a guy who has 18 Morries!) on the advice of a local mechanic who was helping me, and he put them in my box. I put a new stock standard clutch in as well, and she goes like a beauty. The ratios may be wrong I read here, but not that you'd notice ( mind you I have never driven a midget with midget gear ratios), the ratios certainly feel fine. I have had it up to 80 mph, and she cruises along just fine on the highway at 3500 or 4000 revs. I have a Mk 1 Midget with a 1098 10CG engine.
Mike Quilter

For what its worth I have been using a Minor Gearbox in my trials car - Triple last year; MSA Class award 3 years agao with no modifications other than changing the clutch fork and gearbox mounting.

Downside is that the box requires frequent rebuilding due to the layshaft/laygear 1st and Reverse gears rapidly wearing - too much power. Due to the gearing (it is coupled to a Minor Van Diff)I also twist many half shafts!

Upside - repairs are cheap as are replacement gearboxes. It also provides me with a much lower 1st gear and a much more competitive car.

My advice if you want to use the car as a road car go for the 1275 box and spend the money to have it properly refurbished. Gear parts are becoming harder to find and getting expensive

Colin

Colin Weeks

For the benefit of Spridget-tinkerers like myself who may be trying to decide between a number of possible gearboxes ... the part number stamped on the input shaft is quite easy to see (possible even with the clutch release bearing still in the way), as long as the box hasn't had a pattern shaft fitted - two of mine have no number.

Interestingly, though, the 22G229 boxes are not actually '1275' – what they are are ‘B-type gear’ boxes (changed helix angle, as Richard points out above). These boxes were also fitted to all but the earliest 10CC 1098s (HAN8/GAN3). The changeover was April 1964, so the ‘tell’ that many of us use to check it’s a ‘1275 box’ on eBay – whether you can see the wires trailing from the reversing light switch – misses quite a lot of boxes, since reversing lights were only fitted from Sep 67.

Even if your gearbox does have a 22G171-stamped input shaft doesn’t mean it’s necessarily a Minor box. The early 1098 Spridget box also had this input shaft yet has the same mainshaft roller bearings for 2nd and 3rd gears as the 1275. AFAIK the later gear set has never been shown to be stronger than the ‘A type’: in fact I believe the helix angle was widened to make the box quieter, making it theoretically more prone to failure.

However, at the same time the layshaft roller bearings were uprated and these presumably are stronger. The period BMC parts books list these as a direct swap, so might not the strongest Spridget box actually be an early ribcase with A-type gears and the 88G396 rollers?

The difference in ratios is noticeable (even on the road), but not huge:

Mogbox:

3rd Gear: 1.41
2nd Gear: 2.17
1st Gear: 3.63

Spridgebox:

3rd Gear: 1.36
2nd Gear: 1.92
1st Gear: 3.20


Tom
Tom Coulthard

This thread was discussed between 26/02/2010 and 08/03/2010

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