1275 transmission to a 948 engine?

[Larry]

My smoothcase gearbox in my '58 convertible (tourer) is on the way out. I have another ribcase gearbox that went with a 1275 in a Midget. Will the 1275 gearbox hook up to my 948 engine? Which clutch, pressure plate and throw out bearing do I use? The 948 or the 1275 set up?

[bmcecosse]

Welcome to the Forum. These things are better posted in the 'Mechanical' section - a Mod will probably move it soon! The short answer is 'yes' - use all the 948 clutch and flywheel - but you may run into problems with the release mechanism because the Spridget box was hydraulically operated and I 'think' ( ie pretty sure!) it had a different operating lever. I can only say - 'suck it and see'. Complication is that the 948 release lever won't (easily) fit the Spridget box. Maybe someone who actually knows will be along shortly!

[mike.perry]

The flywheel and clutch assembly on the 1275 engine is different to the 948 so you will have to use the 948 assembly with your engine. Apart from that the actual box is externally identical to the 1098* apart from the front plate, release forks, and thrust bearing. You will need to use the 1098 front plate and forks and probably the 1098 thrust.
I would recomend connecting the engine and box and the bare minimum of fittings to be able to test the clutch actuation.
You don't want to bolt the seats in and carpets down then find a problem
* and the reversing light switch

[bmcecosse]

So - do you think the 948 release fork can't be fitted to the 1275 front plate Mike ?

[mike.perry]

I seem to remember from the dim and distant past that the 803/948 and 1098 front plates and clutch forks were not interchangable.
The 1098 clutch forks which are used on the much larger pressure plate do however work on the 1275 diaphram clutch which is very similar in size to the 948 clutch plate. This is because once the rod has been adjusted there is very little movement of the thrust bearing required to disengage the daphram clutch, but a lot of extra load which is why I increase the length of the lever on the relay shaft
All the swaps I have done have been "small boxes" onto big engines. I have not fitted a "big box" onto a small engine.
The only variable is the choice between a 948 and 1098 thrust bearing which should both fit and would affect the rod adjustment.
Someone has to try out all the modifications we come up with or everyone would be sticking rigidly to the workshop manual
so in this case unless anyone knows better I would suggest the minimum re assembly ie 4 bolts to hold the engine and box together, no starter etc, just connect the clutch mechanism and try it out and let us know how you get on

[Larry]

Thanks! You have been a big help.-Larry