Broken Rear Half-Shaft

[Roger Fairclough]

Just forget about the cause and build everything up with new bits and as per manual and it will be fine. Like my friend with wrecked E type engine with brocken inlet valve...impossible as they do not trail open like an exhaust valve and don't get hot or hit by a piston. No wear or seizure in the guide or valve stem etc. Just one of those things. Tempting and satisfying to find a cause but when I've done one mental circuit I give up now.

With regard to the location of the wheel bearing if it is centred in the mid plane of the wheel the weight of the car should keep the bearing vertical even with wear [yes/no?] unless you had spacers on or were cornering on a track.

I've had loads of brocken half shafts for no apparent reason with rear drive cars. They used to break off at the splined end . In the good old days the splines were cut very deep.Unfortunately all stressed metal breaks in the end.

Frank

You didn't solve the problem, you just fixed the result. The fact that you broke so many half shafts, without realising why, speaks volumes for your driving style.

If there is a problem, you find the reason for it. Then you fix the problem and repair the car.

Roger

 

[Roger Fairclough]

Re; the halfshaft design. Surely with a flange on the halfshaft it is designed strong enough to keep the wheel upright. that is what I was tought. If you were to tow the LC around for 50,000 miles without the halfshaft in the bearings would fail? Any thoughts?

Frank

On a fully floating axle design, the hub is designed to take the loads imposed by the static weight of the vehicle plus the much higher loads imposed by the vehicle when in motion. The half shaft is designed to take only the stresses imposed by transmitting the power from the diff. to the hub. The axle on the 70 series uses a semi floating design. In this case the half shaft must transmit power and cope with the bending stresses induced through driving. The half shaft on the 70 series is 32mm in dia.

You could tow the car for a 1,000,000 miles without the half shafts in. The bearings would eventually wear out, you would be bored silly but the bearings wouldn't have failed because the half shafts weren't there.

Roger

 

[Dave Docwra]

The Morris was a 998cc 3 bearing crank. No breakdown cover for pansies in those days. Men were men and girls were men.

Thats my point Frank, most manufactures knew there was a problem & looked for what caused the failure & then a solution, they then changed from 3 bearing cranks to five bearing cranks.

What year the RAC & AA were formed in?

 

[frank rabbets]

I realised why I broke so many halfshafts. I was the original boy racer. Breakdowns due to mechanical failure were very common and most cars had their week points. Morriss Minor 803cc ; big ends, first gear pinions and dif carriers which used to split. It was a cheap car for the masses. They knew the problems before they built the car. Even my mother, who had the car before me split a dif carrier but drove like a pussycat.
My regular trip was to the scrapyard on a Saturday morning but you were lucky to find any 'Minor with a dif or gearbox as someone else had beaten you to it. Rocker gears were so poor and the shafts wore so quickly you had to adjust the tappets every 3000 miles or have a realy noisy engine. No way of fixing the cause which was inadequate oil supply and poor metal. But that is what you got for your money.

Frank

 

[Paul_Driver]

Gosh, this has all become very controversial.

I hope to get my replacement half-shaft tomorrow and whilst I agree that the situation does warrant further investigation, my first priority is the get the motor running again until such time as I can get into a garage to get it looked at properly.

My main concern at this time is why the first replacement half-shaft did't lock into the diff. Yes it was the wrong part, being from an import, but it was of the same length and the splines appeared to be of same shape, size and spacing. When I tried it insert it, it was met with solid resistance and just wouldn't lock into the diff. I think I managed to raise it enough so that it should have engaged.

I hope it turns out well and that the new part will just slip into place. However, the matter that Jon mentioned, that I should have locked the diff first, is bothering me. My actuators are seized anyway so I couldn't. But what are the reasons for locking the diff before removing the broken half-shaft? And if this is the reason for not being able to reinsert the half-shaft - how to get around it?

 

[Dave Docwra]

Hi Paul, the reason behind locking the diff is to retain the locking gear in place, hopefully it will not have shifted & has stayed in alignment, I have not done an 80 diff but someone may be able to confirm my next statement, by removing the actuator you should be able to manually engage the diff lock.

 

[Jon Wildsmith]

However, the matter that Jon mentioned, that I should have locked the diff first, is bothering me. My actuators are seized anyway so I couldn't. But what are the reasons for locking the diff before removing the broken half-shaft? And if this is the reason for not being able to reinsert the half-shaft - how to get around it?

The locking gear is mostly held in place by the drive shaft when it is unlocked. When you take the drive shaft out it's unsupported although held loosly in the lock fork. It doesn't take much for the locking gear to become dislodged and then things get interesting If that happens you will have to try and get it back into place through the end of the axle tube. You can't remove the diff without the locking gear being in the lock position so you can't gain access that way. You can remove the inspection cover and actuator and look at it through there but that may just make it more unstable.

On a diff where the actuator doesn't work, remove the inspection panel and push the locking fork across (towards the diff) manually (before removing the half shaft).

The longer splines are so the shaft can pass through the locking gear and then into the diff. With short splines you would get it through the locking gear but probably not the diff.

If you get the end of the shaft through the locking gear you might then need to raise the end of the shaft slightly to get it into the diff if the gear has dropped a bit through being unlocked.

 

[Paul_Driver]

Well I got it sorted. In the end the diff didn't prove to be a problem and with a little wiggling, the half-shaft slid straight in.

The acid test will be this weekend when I have to drive from Yorkshire to Fairford air show, a round trip of 400 miles.

One last question. What is the recommended torque for the six axle flange nuts?

 

[Jon Wildsmith]

Well done Paul. 25ft-lb for the flange nuts.

 

[Paul_Driver]

Thank you Jon

Thanks everybody