Cornwall Austin Seven Club creating interest in Austin Sevens (1922 - 1939)   

This article, written by John Cockhead, originally appeared in CA7C Seven Focus in March 2006 pp 20-21.

The Half-Shaft Saga
As we left a filling station in Ilminster on our Scotland trip there was a knock from the rear axle and all drive had gone.  My Box Saloon was straddled across the road so it was a quick push into a side turning where we quickly determined that a half-shaft had probably broken!   All you need to do this is to put the car in gear with the engine running and look to see if the prop-shaft is turning, if it is then it is most likely that you have a broken half-shaft. 

We quickly jacked up the nearside wheel and confirmed that the shaft was broken, as the shaft no longer supports the wheel you can feel the whole hub wobble.  Off came the outer hub, in went the broken end of the half-shaft, you may need to rotate the prop-shaft a little before the broken end will push into the axle housing, and in went the magic ball, an approx ¾" (19mm) diameter ball bearing which many of us carry but have never used before. 

Once the outer hub and wheel is replaced then the ball keeps the broken half-shaft from coming back out and loosing drive.  Once the broken shaft is in you have drive again, albeit on one wheel but it is better than nothing.  The only other problem is that the rear wheel with no drive is only held on by the ball race. 

Driving on one wheel is an art, when you accelerate the car slews to one side and to the other side on over-run.  Quite an interesting situation.  There is nothing you can do about accelerating except be gentle, instead of using the engine a s break on over-run dip the clutch and use the car brakes.  We drove like this to Bradford on Avon, approximately 40 miles but at least we were mobile again.  On arrival at Bradford we made a few phone calls and sorted a replacement shaft for the following day. 

At 7.00 am on the following morning we were in the yard of the 'Seven Workshop' and 'Austineers', which by chance was a stones throw from our B&B.  We removed the nearside axle casing and, after removing the good hub as well, the differential and half-shaft slid out without a struggle.  We split the differential housing and extracted the broken half-shaft.  Breakfast was at 8.00 am so we cleaned up and ate.  As soon as the workshops were open at approximately 9.00 am we sorted out a replacement half-shaft, re-assembled the axle and we were on our way again by 10.20 am.  The whole episode had delayed us by just over an hour. 

The 'Seven' had the original half-shafts that presumably were in the car from new in 1929.  These shafts were thinner than later ones and therefore more difficult to find.

Why was I not carrying a spare half-shaft?  I had a brand new one back at home but as I was sure that, being the fatter shaft, it would not have fitted and as we were short of storage space it stayed behind. 

Was my half-shaft loose to cause the break ?  No they certainly were not.  Normally to get the broken stub end of the shaft out of the hub you just hit it with a hammer. Not this one.  All the hammer did was spread the end. Dave Williams put it in his press and after a lot of effort it finally pushed out the broken bit with a tremendous bang and bits on the bench leaping everywhere.  We would never have got it out by the roadside!  The break was caused by 76 year old metal coming to the end of its life.  Metal fatigue!  

D Type Rear Axle Problem
The axle had been “humming” to its owner for some considerable time with a very definite change of note between power on and overrun.  Nothing particularly unusual since many cars exhibit this symptom and continue to run like it for many years.

However on this particular morning the axle appeared to “jam” momentarily before continuing on its merry way!  The owner then thought it sounded a bit noisier than before and there was now a light rubbing noise, rather like a binding brake, that was in time with each wheel revolution.

Having heard the story I knew what the next question would be….”what do you think it is and should I be concerned?” 

Noisy axles are quite common with most of the noise coming from the less than perfect meshing of the pinion with the crown wheel, only to be expected after many years of use and abuse.  More specifically when the note changes between power on and power off mode this suggests that the mesh between the pinion and crown wheel is varying rather than fixed as it should be. This can be caused by a variety of faults.

· The bearings either side of the crown wheel which hold it in position could be worn or collapsed.  Whilst I’d never seen this fault it couldn’t be discounted because the rubbing noise occurred in time with each wheel revolution.

· The bearing supporting the pinion in the end of the torque tube could be worn allowing the pinion to move out of mesh. This is a fault I have seen.

· The bearings on the pinion shaft are secured in position on the shaft by a large nut and lock tab.  Depending on the year this can have a R/H or L/H thread. If this nut works loose the pinion can “wind” itself in and out of the crown wheel ,thus altering the mesh, as you accelerate and decelerate.  I have seen this problem occur quite often so was my favoured explanation.

As a check before we got the spanners out we got underneath the car and found that by using a lever between the propeller shaft flange and the end of the torque tube we could detect longitudinal movement of the pinion shaft which supported option 3 as the probable cause of the noise.

The first thing to do was to drain the oil from the axle and along with the oil came half a mangled ball bearing! Maybe we had more than one problem!

Not wanting to remove the axle completely we removed the torque tube assembly from under the car and retired to the workshop.  Further dismantling confirmed that the bearing retaining nut was very loose on the shaft.  The bearings themselves were complete and serviceable so our mangled ball had come from somewhere else!  At least our diagnosis was partly right!  With the nut now done up tightly the torque tube was replaced, oil added and a short test run.

As expected the axle hum was reduced and there was no longer a change in note between power and overrun.  Partial success but the rubbing noise was still present!

The oil was drained again, the nearside axle casing removed and we were now able to remove the crown wheel assembly complete with differential and half-shafts.

As we pulled the assembly from the axle the thrust bearing on one side of the differential pulled apart and presented us with another 8 mangled ball bearing halves!  Never seen that before but there’s always a first time!  Further inspection showed that tracks on both bearings were badly pitted and the bearing cages were damaged.  The diff casing was thoroughly cleaned out, both bearings were replaced and the axle reassembled.

More oil and then off up the road for a test. The rubbing noise had gone and the owners comment was "its never been that quiet since I’ve had it”.

The moral of this story?

If you hear a noise that you’ve not heard before, don’t ignore it, get it checked before the problem turns into a disaster!

This article, written by Andrew Jarmin, originally appeared in CA7C Seven Focus in November 2007 pp 21-22.

A Nasty Clatter!
Having had enjoyed a Club run through the Roseland we left to head homewards via St Austell.  The Ruby was performing well until we set off up the hill out of Grampound when a bit of a clatter started.

Sadly the opposite happened and it died completely, fortunately by a convenient lay-by.  On opening the bonnet the reason for the misfire became clear. One lead had come out of the distributor cap presumable displaced by the force of the water thrown up in the ford. No problem just put the lead back in, problem solved and away we go. ….only it still didn’t want to go…. There was a good spark from the king lead from the coil but no spark reaching the plug.  A replacement Rotor arm from the tool box was fitted and the engine burst into life.  We were mobile again.

What had happened?  With the lead missing the rotor arm was still offering a spark to the now vacant terminal.  The spark had to go somewhere to dissipate its energy so it chose the line of least resistance which in this case was by breaking down the insulation in the rotor arm. Once it had created a leak path all subsequent sparks took this easy short cut to earth and therefore the engine died. The rotor arm was fatally wounded and is now scrap! An unnecessary death!

The Moral? If you have a misfire investigate and rectify at your earliest opportunity. If I had stopped promptly my rotor arm would be still alive and well. The advice would be equally valid for any other fault that appears whilst you’re driving.  Stop, identify the cause and then make a decision about whether it’s safe, sensible to continue or whether you have to take immediate remedial action.

This article, written by Andrew Jarmin, originally appeared in CA7C Seven Focus in May 2010 p11.