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MG Midget and Sprite Technical - Fitting a smoothcase gearbox to a 1098

Does anyone have experience of getting the necessary clearance inside the bellhousing, to fit an early smooth case gearbox to a 1098 10CC type engine, with its thick backplate and larger clutch? At the moment it fouls badly, and I understand some filing or grinding is needed, but don’t know where. Yes, I made the mistake of installing it all before I found this out!

I’d love to see a picture or drawing to aid the grinding needed, so I can remove only the engine to do it. I’ve heard of actual holes being knocked through the bell housing, which I’d like to avoid!
Thank you!
Andy
A Cross

The smooth case is a weaker gearbox than the ribcase. it also has poorer synchromesh and unless its one of the rare early smoothcases fitted to the mk11 sprite or mk1 midget (948cc) has quite wide ratio's.

Apart from the clearance problem the smoothcase has a shorter input shaft which may be a problem given you have the 1098 backplate. Personally I would try and source a 1098 or 1275 Spridget box.
Bob Beaumont

Thanks Bob. Yes I appreciate it’s weaker, but I happened to have a Sprite mkII Gold Seal recon box so I thought it would get me mobile for the summer.

I’ve had troubles with the rib case I was rebuilding. It needs a new synchro cone surface on the 22G229 first motion shaft, if anyone has one please let me know.

Andy


A Cross

If its an expedient to enable use this year, maybe it would be easier to fit an early type pressed steel backplate and early clutch?
GuyW

Yes that’s an idea, Guy. Something to try.
Another day removing and refitting the engine coming up.
A Cross

The 10cc engine has 59BHP whereas the 948 has about 10bhp less. The smaller clutch may take a bit of a pounding. I may have a reasonable 22g229 input shaft.
Bob Beaumont

IIRC the Spitfire coil spring clutch was used on uprated 948 installations as it had 9 springs rather than 6 and so a higher clamping load. Andy mentioned a 10CC engine which would be 2" mains so I don't think the 948 flywheel would fit though without modification. Another possibility would be to fit a later diaphragm spring clutch to the 1098 flywheel which might gain some clearance, it does require drilling 2 new alignment pin holes in the flywheel. I did this on a tuned 1098 as I found the standard cover wasn't up to the job, I think the cover was a Hillman Hunter which uses a carbon thrust as well and worked well.
David Billington

If Bob can't find you one, I may be breaking a 1275 'box soon, after discovering that the bellhousing had been welded all the way across!


Dave O'Neill 2

Andy

Sell the MkII box and find the less rare ribcase box for your car

Cheers
Mike
M Wood

All this is pushing me more into unearthing that Type 9 that’s even further in the depths of my shed than the Gold Seal one was....

Decisions, decisions! I just want to be driving it!
A Cross

Hi Andy

I am interested in buying your MkII gearbox, perhaps if we can somehow sort an exchange for a good ribcase?

Cheers
Mike
M Wood

Thanks Mike. Distance may be a problem, but please mail me:

My email is
andyspeedbox
at
gmail
dot
com

Bob, if you have a good input shaft, with a bit of “bite” on the synchro ring, please mail me too.

Thanks all, for all the help. You’re a great bunch!

Andy
A Cross

Andy

Thanks - I'll e-mail you.

Cheers
Mike
M Wood

This thread was discussed between 16/04/2019 and 16/05/2019

MG Midget and Sprite Technical index

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