Tale of Woe

[S.J.Szabo]

Well, after coasting on basic maintenance for quite some time, the Trusty Coupe suddenly sprung a fair leak at the end of the left axle tube, soiling its wheel, tire, and my garage floor with gear oil.

After girding my grid, I began diagnostic disassembly to find my worst case scenario was, in fact, reality: the axle bearing had failed (and I just put it in twenty years (and maybe 150K mi.) ago!). Shards from the ball cage ate the seal. Bummer.

So here I sit, elbow deep in rear axle as I take the "opportunity" to deal with some other deferred maintenance issues as well while I ponder the possible wisdom in "if you don't drive 'em, you don't have to fix 'em" (but what fun would that be the rest of the time?).

Sad tale of woe. Yahta, yahta, yahta.... But for me, there's a puchline here; why would the bearing fail? The gearbox drains showed the usual hairs on the magnet, but no chunks. The only debris at the bearing was pieces of cage (the balls seem intact).

So I put it to the very many more learned than I: What could have caused that rascal to self-destruct?

[JTR70]

Sorry to hear that S.J. Nothing worse than the smell of old nasty 90 weight gear oil. The odor can stay in your finger nails for a week or better. Pretty rough for a guy like me whose used to eating with his fingers. I'm sure Bruce will have the correct technical answer but I always assume bearing failer and most other failer for that matter is due to the heat from lack of lubrication. I understand that excessive negative camber will shorten the life of the bearings under normal HWY usage because the oil has to run up hill to bathe them and are quite often starved for oil. Your car is probably stock ride height correct? So this would eliminate that theory. What do you think Bruce? anyone else? Justin

[S.J.Szabo]

You bring up a good point of diagnostic information that I neglected. To be more precise, I run about a quarter degree of negative camber and I'm pretty good about check gear lube levels. The balls are decent looking with no evidence of excessive heat. Also, no changes in the box/axle for quite a while now.

The cages just failed and I can't see why.

All I've got is that the axle nut was seized or way over-torqued (by me, of course). But if this was enough to stress the cages, one wouldn't think it would take over 100K mi. to find out.

[JTR70]

I don't think overtightening would be the cause. Hell, that nut needs to be in the 400 foot pounds of torque range to be right and many are not tight enough. Certainly requires some lever arm and rotational stop (for the drum) to achieve that number. You think it was tighter than that? The cage failer may have just been a defect that finally gave way?? paging "Dr. Bruce"

[roy mawbey]

Interesting view about the torque values. Bearings do need the correct pre-load and assembly for sure. It has always slightly worried me that 1956-59 factory workshop manuals have stated in them lower torque values for rear axle nuts and flywheel gland bolts than is now currently applied by technicians of today.

Maybe I am tempting fate here, but for example my rear axle nuts and bearings are certainly 44 years old or possibly 54 years old never noticed that they have been replaced from receipts going back to the early 60's.
The 90 grade oil I last changed in my gearbox in the 1970's when I put some new split rubber seals on the axles because the old original ones had perished.

When I had replaced the rear wheel brake cylinders with new ones a four years ago I was careful to mark with 'blue marker' the exact position of the nut and split pin in relation to washer. I wanted to repeat exactly the torque applied back in time.

I have my own 3/4 inch socket and breaker bar a nice pole for the lever. After doing the brakes and tightening the nut using my weight and the length down the pole it corresponded easily to the original split pin position on the shaft. I could have gone the extra foot pounds but refrained from doing so. The result since then now seems to work well but of course I do not apply great cornering forces to the car as you might if it were raced.

Why did the factory arrive at lower figures of torque? SJ what torque did you apply and what tools did you use. Yes, bet Bruce has the answers

Cheers from 'head in the sand Roy'

Attached a few pics of my home made tools

[roy mawbey]

SJ,

It was a nice afternnon decided to look at the factory manual over lunch in the garden. Your bearing must have been fitted well by yourself to last 150K miles. After reading my books including also the Elfrink 1965 version the following was clear at that time:

1). The torque values for the rear axle nuts was 260 ft lb and the same for the flywheel gland bolt. Thats a lot of difference to the 400 ftlb used today for both items. I really wonder why this changed as the factory was well into racing in the 50's/ 60's.

2). The bearing cover with the 4 bolts has the seal you mention. They make particular mention of the fact it has to be installed square otherwise it will leak oil.

3). The use of shims might be needed when the distance between the brg flange and the bearing cover is measured. These shims come in 0.004" thickness and the unit has to be bolted up to check. Compression of the parts is considered to be 0.004" You then make up the required number of shims.

The assembly is involved even down the correct bearing puller, you must have done this correctly for it to last so long? Its as though the bearing became loose axially and this destroyed the seal for you to see the oil on the floor. Just maybe you had not quite enough torque on the axle nut which slowly made the bearing suffer?

Interested to know for certain what made that happen. You really have a driver, I call mine a driver but I don't do the milage you seem to manage. Added 30 miles to mine this morning. Went to Goodwood the queue to get in was so long I turned round and drove home the long way round.

Roy

[S.J.Szabo]

You shoot a good illustration foto, Mr.Mawbey.

The torque value issue has been discussed many times over the years, but I believe the intended value is about 400 ft/lb. I had thought that I had achieved that value when I last assembled it, but it took much more than that to break it loose (and in fact, it took several turns to actually become "loose"). There was no axial play in the axle before dis-assembly.

Inspection of the nuts prompted me to obtain a fresh pair tho.

[JTR70]

An afternoon in the garden having lunch sounds like a great day Roy! Thanks for the great photos and details. I like your tools BTW! My theory on the torque values being raised through the years was perhaps from real world driving feedback showing prematurely worn splines? Just a theory of course.

Are you now in process of putting your axle assembly back together S.J.?
Justin

[S.J.Szabo]

Well, I'm muddling thru it. Once you dig this deep, you look around at the other issues that should be addressed while you're there; clean, a little paint, kits for the rear calipers, new boots, etc.

It'll be a "work in progress" for a little while, I reckon. Thanks for asking.

[JTR70]

Be careful! That can quickly "snowball" then before you know it the whole drivetrain is out...