Morris Minor Owners Club

Something that's been on my mind for a while now that I've always wondered - What is the weakest part in the 1098cc drive train from the engine back? Any ideas or opinions welcome!

Probably the half shafts.

I've had half shafts fail, but never anything else (touch wood). The weakest item is probably the driver and how they use the car.

I Suspected it would be that half shafts, I just wondered And maybe I should have said besides the driver!?! This begs the question though any idea how much power could a standard 1098cc drive train take with uprated shafts or even a different rear axle? Obviously there's a lot to take into account but lets assume that the car will be pushed fairly hard, what type of power (Torque, Horse power/KW) do you recon it could take for any sort of sustained period?

There are so many variables and not many certainties. I have never had a half shaft fail - even when I had a fairly well modified 1340cc Minor which was used on the road and for occasional sprints, hillclimbs and autotests. That car ran with a standard rear axle and standard half shafts and used a variety of differentials over the years but all of standard design.
On the other hand, my wife broke a half shaft while out shopping in her completely standard car .

I would agree that the standard half shaft especially if the half shaft has completed a high mileage is the weakest point in the transmission chain.

Sudden shock loading of the half-shaft is what takes them out i.e. lifting a wheel and dropping it down can lead to half-shaft failure.
A pair of traction bars will reduce the possibility of wheel lift and as importantly wheel hop.

Improved strength half-shafts are a must if considering driving hard.

My own half-shafts were standard NOS items until heat treated and were then guaranteed to cope with 173BHP.

They have over many years have coped well without failure delivering 140BHP to the road surface. The axle is well located and uses traction bars to eliminate axle hop.

I would agree with the halfshafts, having broken three of them over the years in my 1275cc MG Midget-engined Traveller. I have also managed to wear out or damage at least two gearboxes also (usually 1st/2nd gear), during my ownership since 1989 and with the car now on 162,000 miles.

Living out in the sticks with very rough country roads, potholes and speed humps everywhere and some steep hills doesn't help.

I now keep spares of each.

If you keep spare half-shafts make sure that you keep them handed and do not use them on the other side of the axle as half-shafts get wound up sic. in use and if you reverse the wind up they will snap.

Second gear dropping out on the overrun was the one I had

Having been guilty of installing an upgraded the engine without consideration about the drivetrain, it's definitely the gearbox next, then the rear axle last.

With a racing a- series installed the clutch ate itself. With a better clutch installed I went through gearboxes like no-one's business. Eventually I upgraded the rear axle. This as out of precaution, not necessity.

With all said and done then, if one wanted to replace the rear axle (Theoretically) with another axle assembly (Diff and all), what would be the options? Or perhaps I should say the easiest options?

The easiest option is to upgrade the half-shafts.

When you increase the engine power you move the weakest point in the transmission further down the drive train.
For example:-
Upgrade engine - clutch fails, upgrade clutch.
Upgrade clutch - gearbox fails - upgrade gearbox.
Upgrade gearbox - back axle fails - upgrade back axle.
So the cycle continues having carried out the upgrade cycle more times than I care to think about and having spent much more money and time than I should have done.

So now have a 140bhp 'A' Series engine with a very capable racing clutch mated to a Quaife CR/SC gearbox and an uprated Minor rear axle.
So far it has all kept together and with 7" very sticky racing slicks on the back.