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MG MGB Technical - Rear wheel play?

I'm still chasing a clunk from the rear, having already changed all the thrust washers in the diff, and the U/Js in the propshaft, I turn my attention to the rear hubs.

With the rear wheels off the floor, I can feel definite play in the wheel (rostyle) when I hold it at 12:00 and 6:00 and try to shake the wheel. Both sides seem the same. (I am quite a strong boy however!)

When I pull the handbrake tight on, there is no play.

The hub nuts are done up to at least 150 lbft, as I have tried to re-torque them with no movement.

The previous owner told me that it had had new bearings.

What could he have done wrong?
If he fitted the spacer wrong way round or not at all, could the bearing or hub still be loose, yet torque up properly?

I guess if it is play in the hub that when I undo the hub nut I will be able to pull the hub off with my hands?

I suppose the best idea is to get a pair of wheel bearings and make sure that they are fitted properly.

Should there be some rock in the bearings, are they just a single row ball race- I would expect that to rock!

Martin Layton

Update.

The bearing is fine. The Haynes that came with the car has oily marks on the axle page, so he likely followed the instructions.

I've changed one bearing anyway, as I had to slide hammer it apart with great force, to check if it was assembled correctly.

The play seems to be in the hub, which did just drop off when I undid the nut.

The hub sits between two tapered cones. One is the oil seal inner, and the other is a conical washer under the nut.

Except they don't lock.
The hub is too thin, or the bearing is too thin (more likely), and the outer cone must be bottoming on the splined portion of the shaft.
What I need is some shims between the oil seal cone and the bearing (that I don't have. I did think of cutting up a tin can but that is going to be difficult!)

The whole thing seems rather a daft idea really.
Martin Layton

Update on the update.
Exactly the same play...

b####r!

Waste of half a day and £13.

According to the archives, this happened to a Dave Brown in 2000, but the thread doesn't reach a conclusion.


I suppose I will have to see how much for a second hand axle to rob the hubs off, compared to new hubs and spacers.

I still can't see why it doesn't work, even if the hub is worn, you would have thought it was tight enough to take out any play.
Martin Layton

Daft? I don't think so, problems with this arrangement are extremely rare, which is why you can't find any info on fixing it.

The single row of balls isn't going to contribute to movement in a good bearing as there is another just the same at the other end of the shaft - unless there is wear/play in either bearing of course which allows the half-shaft to move in and out or up and down ... or both.

There is a spacer that goes on the half-shaft before the bearing, with a flat face and a convex face. The convex face must face the shoulder on the half-shaft. You don't mention this in your subsequent posts. The bearing is a heavy interference fit on the half-shaft (usually needs a press to get off and on). The oil seal collar slides onto the half-shaft after the bearing, and this has the inner taper for the hub. The bearing is a light interference fit into the axle casing, protruding slightly, and the bearing cap/oil seal carrier has a recess to accomodate this protrusion and clamps the bearing outer against the axle casing. Short of the bearing inner moving on the shaft, this clamps the half-shaft rigidly from an 'in and out' point of view, whilst still allowing to rotate freely of course. With the tapered out washer and the nut torqued up the hub should be very rigidly clamped, and usually needs a puller of shock to free it from the inner taper even when the nut and outer taper has been completely removed.

Really you need to rmove the back-plate and bearing cap, then pull the half-shaft out of the casing, and check the inner spacer is in place (if you haven't already).

If the bearing spacer is missing when you tighten up the hub nut you will tend to push the bearing further down the half-shaft than it should go. As load is placed on the wheel and it rotates this will tend to push it further still down the half-shaft. Doesn't take much of that to release the clamping force on the hub which will then rock. Either that or the bearing inner is too narrow. Is the bearing cap an interference fit onto the bearing? It should be. Or the hub is the wrong one or has been fiddled with. I wonder why the PO fitted new bearings - perhaps because of this play which is due to something other than bearings.
Paul Hunt 2

Thanks for the reply Paul.

I pulled the shaft, and changed the bearing (It did need pressing off, and driving on), checking that the spacer between the bearing and shaft was the right way round. Once pulled off, it is obvious which way the spacer goes, there is an marked radius on the shaft that the concave face of the washer covers up.

The only marks on the old and new bearing is RMS-10, the old one is 0.873 thick, the new one measures 0.875" exactly (7/8" sounds a likely size to me!)

Both taper washers have machined splits in them, 2 in the oil seal washer, and one in the nut washer, so that they can compact into the tapered bore and lock to the shaft.

I did think that the outer washer was bottoming on the splines, but careful examination of the hub shows that the splines are inside the hub slightly, so it cannot be.

Even with a slightly wrong taper the clamping force from the hub nut should distort the hub enough to lock it up tight, how else can I get 150 ftlb at the nut? Something must be going tight.

I suspect the PO was trying to sort out the clonk from the axle, as on my test drive, I remarked on the clonk, and he told me it had just had new wheel bearings. (And I thought "I know what that is- thrust washers!")


I'm starting to think that I'm chasing the wrong end of the shaft, and the hub is locked, but the diff end is lifting when I shake the wheel. Both sides seem the same, and I wouldn't call the axle noisy, it has only done 90,000 miles.

I have been inside the axle, to renew the thrust washers, and the crownwheel wasn't loose, neither did the sun wheels seem unduly loose, but I wasn't looking for a problem other than thrusts then.
The splines at both ends of the shaft seem fine, but I suppose it doesn't need much wear to produce play that I can detect.

Looks like I may be swapping the axle if it fails the MOT next month, but it would probably be a good idea to try and pull someone elses wheel off to see if I actually have a problem!
Martin Layton

The hub tapers can wear from running loose, and many are. That in turn wears the splines. However, it should still lock up when tightened, if not it is usually that the nut is bottoming on the thread end runout/shoulder. I have sometimes found it necessary to fit a washer between the nut and taper collar to cure this. I put a thin coat of Permatex #2 on the inner collar - not on the tapered bit - between the collar and bearing to prevent oil leaking under the collar. Then anti-seize on the tapers, splines, and threads and nut face, torque to 150. Correctly done, the tapers themselves would drive the car without splines.
Another source of "clonk" that I keep posting and nobody acknowledges is a loose nut on the gearbox output shaft - sounds just like the RAX noises, and is commonly but not always associated with speedo readings that develop a sort of "high limit" = won't go over 60mph when warm.
FRM
FR Millmore

Thanks FRM.

Seems obvious now, but I never tried driving the nut all the way down the threads. It might get tight at the bottom- it won't take long to make up a flat washer to check (I realise that it has to be smaller than the tapered washer so it will go inside the hub). Something to do tomorrow (last day of holiday)


I have checked the gearbox nut as I have renewed the oil seal already.

I even changed the gearbox mounts in case it was lift in the back of the gearbox causing a knock from the splined part of the propshaft. (Yes the spines are likely worn, but not as much as on my "spare")

Tip for anyone else interested: if you file the single bolt holes in the crossmenber cradle upwards into slots you can bolt the rubber mounts and centre peg frame solid to the gearbox, then just push the crossmember back on, bolt up to the chassis, lower the gearbox, which will then drop the pins to the bottom of the slot (exactly where the original hole was) and then fit a large washer 'twixt nut and crossmember and tighten. I managed to change mine without dropping the exhaust as well.

Will report back tomorrow...
Martin Layton

To get detectable play at the wheel from problems at the diff end the play there would have to be *very* significant, I would have thought. The fact that the hub 'fell off' the half-shaft does indicate to me that, for whatever reason, it wasn't being clamped between the two tapered parts. That *should* be visible as movement between the hub and hub nut/tapered washer. For both sides to be affected there must be two identical problems, as the half-shafts are separated of course. This says to me 'incorrect parts' somewhere in the system rather than wear. I'll be interested to hear the effect of a thick washer between nut and tapered washer. In terms of bearing tolerances 2 thou difference between the old and new bearings seems a huge amount to me.
Paul Hunt 2

Paul-
Cars with one side loose were usually fooled with by the same guy on the other side - so it is v common for both sides to be the same. I rarely find a hub tightened anywhere near 150 - maybe 25 is more common, and I've unscrewed some with my fingers after removing the split pin. If they run like that for long you will get the wear. But other than fitting the washers, I've never had to resort to replacing parts.
FRM
FR Millmore

Success!

With the addition of washers (thanks FRM) and a bit of radiusing on the inside of the outer washer I have eliminated the play.

I think the problem was actually the outer washer contacting the radiused shoulder of the halfshaft, where the thread runs out. I guess both hubs are worn thinner than they should be. Without the washer, when tightened, the split pin hole was right at the top of the castellated part of the nut as if the nut was 1mm too far on

It would have been easier to fit shims between the bearing and the inner conical washer. (as long as the oil seal still has room to run on the straight part of the cone.) Next time I mess with the back, I will get something made up, as I have a spare bearing for the sizes.
Martin Layton

Martin-
Great! Anytime a split pin hole is above the slot bottom by any significant amount it indicates something worn or missing. Fitting shims between the bearing and inner taper collar is fine, and it gives you a new seal track in the bargain.
FRM
FR Millmore

Glad to hear you have fixed it. I checked my old axle this morning and without hubs the nut with outer washer in place will screw down so the split pin hole is almost entirely above the top of the nut, i.e. the nut is able to screw down much farther than it should do with the hub in place. With the outer washer removed the nut went down even further, and the split-pin holes were completely clear of the castelations in the nut. This is probably at least 1/8" if not 3/16" further down than it should be with the hub in place.

My roadster was certainly at 150lb or thereabouts, I had to take it to a garage to get a 5 ft breaker bar on it to undo one side. I had to convince the mechanic that it was a normal right-hand thread as he wanted to 'undo' it the other way. Not only that but it was the left-hand anyway! Heaven save us from 'professionals'.
Paul Hunt 2

This thread was discussed between 11/04/2007 and 14/04/2007

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