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MG MGB Technical - 1974 with Axle problems

I have a 1974 B roadster with rostyles wheels. The axle is of an unknown age but is more than likely form a rubber bumpered car because of the location lugs for the anti roll bar.

Last October I had the local ‘specialist’ renew the small washer that stops the axle clunk on take up of drive. However this did not stop it clunking and when I question him on it he said that I have a tapered bearing although clunks is with in tolerances and that I should not worry about it. Since than the clunking has got worse and to add to that the right hand wheel (as standing behind the car) has developed a wobble. I have not covered more than a few thousand miles since October.

To try and see where the problem lay I have done the following things:
Looked at the tyres - there are no unusual wear markings on the tyre. I have changed wheels and brake drum. Ensured the centre nut is tight. I have stripped the rear hub assembly down to try and ascertain if the bearing was worn. I could not tell if this was so. I have run the car with the rear wheels off the ground. I could see the wobble. I took the wheels off and run the car this also showed up the wobble in the hub.

The symptoms are:
No oil leaks from the axle on or near the hub in question. I can feel the wheel wobble only when I am braking or travelling very slowly, but I know that does not mean it is not there. Nothing seems to have cured the wobble
Now for the questions…phew I hear a few of you say!

1) How to I ascertain the hub bearings are in good shape?
2) What other things should I look at to try and stop this worrying problem?
3) Could it be the prop shaft out of true? If so how can I tell?

Thanks for you help
Ian


Ian Holliday

Ian. You have an interesting problem and, unfortunately, one I am not very knowledgable about. However, my thoughts may give you something to check out until someone who has more experience chimbs in.

First, an out of alignment or out of balance drive shaft normally shows up at the drive shaft, rear of the tranny and the rear axle pinon. When you put the car up on jack stands, run the engine with the tranny in gear and, very carefully, crawl under the car and look at the drive shaft, you should see it wobble from side to side if there is an out of balance condition. Take a look at the workshop manual to see what the yoke alignment should be and compare to what you have. Tom Sotomeyer has written a draft article on U joints and yoke alignment for my website, but it will be several weeks before we can get time to post it. E-mail me if you need a copy before then. A driveshaft-U Joint problem should not show up as rear wheel wobble.

Wear on the wheels, where the studs and nuts go, can cause a clunk when accelerating and braking. If the holes in the wheel are oval, the wheel needs to be replaced.

Axle bearings are inspected by removing and examining them. When we lived in Spain, the roads were not the best and a lot of them were cobble stone. Rear axle bearings lasted a relatively short time and I remember having to help my father replace them twice in three years. This is normally indicated by a growling sound from one or both sides of the rear end. By driving the car somewhere where you can turn it back and forth as you drive, you can load and unload a front or rear axle bearing. If the sound changes with the turns, it indicates an axle bearing problem.

A wobble in a rear wheel normally indicates a bent axle shaft. I once spun a Mustang trying to avoid hitting an idiot who pulled in front of me on a wet road. The right rear wheel hit the curb, bending the wheel and the axle. Car was drivable using the spare, but there was a distinct wobble to the wheel. Pull the wheel and brake drum and put a dial indicator on the hub to see what your run out is. Ideally, zero run out is the best. However, most will probably show .001"-.003". If it is over .003", you need to replace the axle because it is bent. When I had the Mustang, I had a room mate who was a mechanical engineering student. He told me that running a bent axle would cause a cyclic vibration which would damage the rear axle bearing. So, if this is true (I was a sociology major and ROTC cadet at the time), replacing an axle with excessive run out will both save the bearing and provide a somewhat safer ride. Being a poor student, I could not afford to do this for some time, but the rear tire did not show excessive wear due to this wobble. Perhaps driving style had something to do with it as the tires did not seem to last very long. With the better tire technology today, you might, or might not, have the tires show up some form of wear from a rear axle wobble.

Sorry I cannot provide more assistance. Les
Les Bengtson

Hi

Why not swap out the entire axle and be done with it. Probably what you will have to do in the long run after you change all of the misc. parts and the time involved. Axles are dirt cheap anyway. Maybe get a 78/79 low mileage unit. Alan
Alan

Ian, check to make sure all the u-bolts are tight. On top of the axle there is a pedestal that has grooves that hold the u-bolts in place. Make sure that those grooves are not wallered out, allowing the u-bolts to wobble. You should also inspect all the rubber bushings in the rear suspension.
It's possible that you have a bent wheel, which may not be the cause of the problem, but is distracting you from the real cause.
Have fun!
Ken T
Kenneth Thompson

Take a look also at the rear shock bolts.
glg gimbut

Les.... thanks for your helpfull comments.
Yes I would appreciate the details about U joints/yokes my email address is doc_ian@hotmail dot com....sorry about entering it this way but I get alot of spam as it is and i this will help keep it down!
I can't help thinking that the half-shaft is bent too. But as I said there is no oil leak which would indicate this.
Unfortunalty Alan axles here in The Netherlands are not cheap or in plentiful supply. Neither is the car garaged so undertaking that sort of work in the road is not really an option.
Thanks for the other comments.I have looked at the wheels and tyres but I have aalso run the car without the them (suported!) and without the brake drum too so it would seem to be a half shaft or bearing or propshaft...but it would seem that the later can be ruled out.
Any more help is appreciated. I am off the the classic car show at Rosemalen now.
thanks again to all
Ian Holliday

This thread was discussed between 14/03/2003 and 16/03/2003

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