No drive.

[ferret76]

I just got towed home. Stopped at an intersection, into first gear to move off. Just as I was adding a bit of revs and releasing the clutch there was a metallic bang followed by a complete loss of drive. Engine seems be running fine and I can still select all gears. With the clutch pedal out there is a mechanical scraping noise but no drive whatsoever. I'm thinking something catastrophic has happened in the clutch. The loud bang has me mystified. Any suggestions?

[Rasputin]

Half shaft has broken.

[ferret76]

Thanks for your reply, I'll check that straight away.

[mike.perry]

Handbrake on, engine on, make sure that the car will not roll, in gear and see if prop shaft is turning. If so then yes half shaft broken. Jack up back wheels and you should be able to feel which shaft has broken when you turn the wheels

[aupickup]

halfshaft or clutch

[DAVIDMCCULLOUGH]

I had a halfshaft go on the way to last years national rally, simple click as I moved away from a petrol pump and no more go. We pushed it over to the side of the garage and when I tried it again the speedo was reading 30mph while stationery with the clutch out. The car was recovered to the rally field by the AA were we were able to buy all the parts and fit on the Saturday morning!

heres a link to the story then with a pic of the broken bit.

http://www.mmoc.org.uk/viewtopic.php?f=4&t=50803

[ferret76]

Here is an update just for completeness:

Right hand half shaft broke right at the hub end. On closer insepction it would appear that this was the result of a dodgy weld holding the end piece to the shaft. A repair to a previous break perhaps?

I am in the process of 'borrowing' a second hand shaft from a donor car and hope to have it installed, new seals etc this weekend.

Thaks all for your input.

[MarkyB]

Unusual place for it to break, I wonder if it's an "uprated" half shaft?
Seem to remember some comments about the quality of the welding on them.

[philthehill]

See:-
viewtopic.php?f=4&t=53493

[Roni]

I have just had the same thing happen. Flange end of the half shaft sheared off. Before I fitted the two spares I had, I had them crack tested. Both were cracked in the same place as was the other shaft. I found new ok replacements, one a NOS one.
What caused it looks like it being a stress crack caused by play in the hub/bearing/axle stub area. The hub had in/out movement and was able to wobble. The bearing had become a loose (finger pressure) fit in the hub and axle stub. It was also only 5000 miles old and did not have a lot of play.
Different hubs, axle casing, bearings and half shafts seem to have fixed it. Finding out how to assemble correctly helped a lot too. It is good to have knowledgeable experienced people around who don't mind being asked a lot of questions.
The axle gasket needs to be the correct thickness, 0.2mm, to enable the half shaft flange to clamp the bearing outer race correctly in the hub. Supplied gaskets were 3 to 4 time thicker than this and would enable in/ out movement of the hub, possibly causing wear.
The inner race is clamped on the axle stub by the central nut which needs to be tightened sufficiently. If not, movement can result also causing wear. I found reference in a manual to a minimum of 180 ft/lb for this nut. My latest tool purchase is a 1 7/8 socket. Makes life easy.
The correct bearing needs to be used with the correct clearance. C3 seems not to be adequate in this application. Originally it seems to have been a CN clearance (= C2.5).
Hopefully this failure wont be a more common one as components get older and re-assembly practices become more varied.

[philthehill]

I would be wary of the 180 lb ft quoted.
There is no torque figure quoted in the BMC Minor Wksp manual and that may have been omitted on purpose.
In the special tools section 'Q' it quotes the requirement of a torque wrench (Pt No: 18G372) of 30 - 140 lb ft. NO higher.
The nut should be done up as tight (using hub nut spanner Pt No: 18G152 or similar socket) as you can get it with normal effort.
I use a socket and breaker bar of 14" length for the purpose which is adequate and has never failed me yet in many years of repairing Minors.
I would suggest trying the way I have described above and then see what torque reading is required to exceed your tightening . Please let us know what reading you get.
Better to be safe than sorry.
As regard the socket you have purchased - ensure that the nut face is not recessed/concave which reduces the contact with the nut. I ground the recess/concave away on my socket to maximise the nut contact.
You are right about the standards of parts these days but you may be consoled to know that it is not only parts for Minors where poor quality parts can be found, it ranges through all parts for all marques.

[bmcecosse]

It does indeed seem to be a 'bearing' problem that is causing these previously 'unheard of' shaft failures. I would also be wary of that gasket thickness - I understand it should 4 thou = 0.1mm thick to clamp correctly - with the rubber O ring to make a good oil seal.

[philthehill]

ferret 76
In one of the posts above you mention the weld had broken.
Would it be possible please to post a photo of the offending item especially in the area of the 'weld'.
The reason I ask is that there should be no weld between the axle shaft proper and the flange on a stock item but some uprated half shafts appear to have had the hub flange welded on which is a totally poor practice.

[Roni]

This may be of interest -
http://www.mgaguru.com/mgtech/rearaxle/ra102.htm
It explains it better than I can. It also lines up with what I was told by the experienced old time mechanics and specialists, some with 60 years of it.
Parts quality? It took 4 bearings to get 2 that worked. The first fitted had play evident immediately with no distance travelled. Enough to potentially fail a safety check as "play in bearing."
The socket used has been modified to give maximum contact with the nut faces.
I tried re-assembling the hub using the method used before the socket and then looked at the torque to move the nut with the torque wrench, 40lb one side and 60 lb the other. "The nut should be done up as tight (using hub nut spanner Pt No: 18G152 or similar socket) as you can get it with normal effort". What is normal effort? It must change depending on the person. When I worked at a truck tyre shop I found the drivers' definition of tightened wheel nuts varied greatly, from just beyond hand tight to tight enough to shatter an impact socket and break lugs.
The gasket thickness was quoted in the manual I have. If the hub is assembled with the bearing and halfshaft and no gasket the resulting gap was 0.010" - 0.012" on my hubs. The gaskets supplied from a usual UK supplier measured 0.035 -0.040" thick. Great for providing a good oil seal but not so good in letting the halfshaft flange touch, let alone clamp, the bearing outer. I must ask their opinion on this.

[bmcecosse]

The tightness of the nut is not really important - as long as it is 'tight enough' - the direction of rotation will keep it firm - even if the lockwasher fails. It has no 'bearing' on the fit of the hub bearing! Certainly 35/40 thou is ridiculous.... The 'gap' would need to be measured with wheel nuts tightened to the correct 35 ft lbf torque -using maybe thick washers in place of the drum and wheel....

[philthehill]

With respect the link quoted refers to a MGA axle which is different to a Minor one and may require a higher torque figure because the axle tube is of larger dia. If they were the same nut I could accept the torque figures but they are not.
MGA R/H hub nut Pt No: 1G7582
Minor R/H hub nut Pt No: 2A7103.

Normal effort means that you do not put a scaffold pole over the breaker bar or hammer the end of the breaker bar to get the nut tight. This is were a bit of common sense comes into play.

Only from car No: 376869 does the L/H hub nut have a L/H thread. On the traveller from car No: 370228.

I disagree with bmc on this one. The nut does have to be tight. Even though it may have a supposedly self tightening L/H thread it does not work like that; the nut will be loose (not as tight as intended by the manufacturer) and will lead to accelerated wear.

[bmcecosse]

I DO say it needs to be TIGHT - just not stupidly tight!

[philthehill]

bmc
That I can agree with and to me 180 ft lb is way too tight. In fact I could not do the nut up that tight as my heavy duty torque wrench only goes up to 150 ft lb and most 1/2" drive ones will not exceed that reading anyway.
Next time I have a Minor hub nut off I will tighten the nut to my usual loading and see what torque relates to my tightening.
I will also speak with my neighbour who has a MGA and see what torque he sets his hub nuts to.
Phil

[Roni]

I have to admit I didn't tighten up that much but the nuts are still tight. It seems that now days the meaning of "tight" is quite variable. The people who really knew are getting fewer.
The person at the engineering shop I bought the rear bearings off made a comment at the time. "These are the same as my MG uses, same hubs." He would know what Minor hubs look like, he has decades of competition experience in Minors. He confirmed the hub nuts need to be tight.

[bmcecosse]

Any nut or bolt is designed to be 'tight' in use. But 180 ft lbf is madness - it wouldn't surprise me if the thread on that v thin nut would strip out at that torque! 'Tight' is enough and then locked over. There is no great tendency for that nut to come loose. Has anyone ever opened up and found the nut loose?