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MG MGA - Rear axle leak

I have a 1956 MGA, and both rear axle shafts are leaking into the brake drums. I've found a number of historical threads on the subject, which have been very helpful, but I still have an unanswered problem -namely, that having removed one of the rear hubs, and extracted the bearing (it takes a brave man to attack it with a clump hammer, but I really didn't have any other option)there is a thin shim sitting between the bearing and the back of the hub housing, which isn't shown on any of the component diagrams I've seen. Moss doesn't show it, and neither does my workshop manual. Having said that, I don't have any O-rings, so I'm presuming this was just an earlier design. Can anybody confirm that please?
Also, I've got one other question when the time comes to reassembling it. Does some of the axle oil slip through the oil seal to lubricate the bearings? If so, is it only the paper washer which stops it getting into the drum?
R J K Sinclair

Mr. Sinclair,
Look in this web site
http://mgaguru.com/mgtech/rearaxle/ra1.htm
/ gil
gil

Thanks. I've already looked at that link and found it very useful, but it doesn't mention the shims that my car has - hence the question to a wider audience.
Robert Sinclair

Robert

Clausager makes refernce to earlier 1500 axles that had both half shafts with R/H hub lock nuts. Later these were handed and the O ring introduced.

The workshop manual shows your spacer on the outboard side of the bearing (Diagram H2). It also does not show the O ring.

Steve
Steve Gyles

The shim is non-standard and does not belong there. The assembly parts around the bearing are (supposed to be) precision machined to provide the correct depth to match the width of the bearing with no shim required. Adding a shim at that location would hold open a gap at the outer gasket surface which would allow oil to leak into the brake drum. If the hub assembly dimensions do not match the bearing width, you have at least one faulty part. Measure everyting carefully.

Very early production hubs had no o-ring, only the paper gasket. This is not well documented, and is not shown in the Service Parts List. Parts with or without the o-ring gland are interchangeable with the early one being superceded by the later one.

I have never seen one of the early non-o-ring hubs. Considering that this is not documented in the SPL, it is possible that hub may have had looser machining tolerances and may have needed a shim.

Differential oil does indeed run through the tube axle housing into the hub to oil the bearings. Since the hub interior is larger diameter than the oil seal working surface, oil forms a puddle in the hub leaving part of the seal lip below oil level. If the seal goes bad it will leak profusely.

If a new seal leaks after only a short time in service, the mating surface on the axle housing is most likely worn. This is very common after decades in service. The fix is to install a Speedy-Sleeve or Ready-Sleeve to repair the worn surface.
Barney Gaylord

The only things that seal the back axle from the rear brakes are the oil seal, the O ring and the paper gasket.

I have found that a small coating of gasket gunk is a good idea to help the paper seal. The O ring groove often seems to get damaged with people pulverising the nut with a BFH and chisel, and it's important that this does not have any raised edges, otherwise the thing will never seal under normal use. The same is true of the big ring that sits in the hub between the O ring and the big nut.

It's important to check that the surface onto which the oil seal seals is free of grooves and rust. In emergency I have used an oil seal with a smaller ID to get a seal while waiting for correct parts to arrive. If the surface is rusty or grooved, a speedi sleeve is a possible cure (but I opted for a good used casing from Bob West instead). If rust is minor, then fine wet and dry followed by polishing paper does the trick.

I kept my (marginal) axle in use for more than 15 years, but now the car is leaking oil from every seal in the axle, plus teh gbx rear seal, plus the backplate-engine gasket, so everything is coming out for a major seal replacement exercise (people have been referring to my car this summer in the same terms as the Torrey Canyon).

It is also essential to make sure that the big nut is tight, and that the locking ring is used. I found a big bed spanner in a junk shop with needed minor adjustments with a file to make it fit the nut.

To pull the hubs, a slide hammer costs a few pounds (I paid less than 20 Euros for mine) and does the job in seconds with no damage and stress.
dominic clancy

Thanks guys, that was all very helpful. One final question - are there any tips for getting the bearing back inside the hub unit. I don't want to resort to my trusty hammer again, but at the moment it's threatening to be just as obstinate going back as it was coming out!
Robert Sinclair

I'm always looking to increase my special tools collection. Do I need a clump hammer? or can I make do with my BFH and Birmingham screwdriver? I've never come across a clump hammer before.

TTFN

Derek Nicholson

Robert

Are you certain that you have the correct bearings fitted. i.e. the fact that a shim had been fitted may make it prudent to check the bearing number.

Just a thought.

Steve
Steve Gyles

I think RJK means "lump" hammer - a colloquial term for a hammer with a weight of 2lbs or more.
Cam Cunningham

Brings back memories. My first encounter with an MG was because of this very problem. A man in my home town bought a new MGA around 1958 and had problems with leaking axle seals. There wasn't an MG dealer for many miles, so he brought it to my dad's Studebaker dealership for work. Don't know why he thought we would have any idea of how to fix it, but he was a good customer and dad's mechanics did their best. I still have fond memories of that Iris blue roadster that started a life long interest in sports cars for me.
Bill Young

Hi Folks. I have an early MGA 1500 roadster. My rear axle does not have O ring seals like the later models do. I can confirm Barney's statement that there should not be a shim under the bearing, since I had my rear hub apart recently to cure an oil leak. For people needing to remove the rear hubs from a non wire wheel car, but not having an extractor or slide hammer available, this crude method works: Get a short length of chain with links big enough to fit over the wheel studs. attach the ends of the chain to a pair of kittycorner wheel studs, using two lug nuts to hold the chain ends tightly in place on the studs. Now find a heavy weight, like a big rock or old starter motor. Place the weight in the center of the chain. Now use the weight as you would a slide hammer. Let the chain go slack, and then pull the weight outward from the car. Several light "pulls" will do the trick. The weight's inertia will easily pull the rear hub. As with most "emergency" type fabrications, this setup MUST be used with extreme caution! Do not allow your fingers to become trapped between the weight and the chain! Do not allow the weight to hit your body when the hub comes free! As an additional safety precaution, a longer chain could be used, with the additional length being used to wrap around the weight. Again this is an emergency technique to be used only when the proper tool is simply unavailable. I used this makeshift "puller" years ago on an MGB that I owned, and it worked great! Cheers, Glenn
Glenn

How about sealed bearings? Pros/cons? Marvin
Marvin Stuart

Hi Marvin. Are sealed bearing with the proper dimensions available? I have never seen an MGA or MGB rear axle with sealed bearings, although it is an interesting idea! Cheers, Glenn
Glenn

To install the bearings in the hubs you need to ise a hydraulic press (your local garage will probably have one) or use a piece of metal tube of the same diameter as the bearing, and a vice. To get the hubs onto the axle casing, the piece of metal tubing and a BFH with some light persuasion usually does the trick.
dominic clancy

Hi folks. Installing the bearing in the hub can be made considerably easier by heating the hub, and cooling the bearing before installation. To heat the hub without damaging the rubber seal, put the hub in a large tin can, then put a 100 watt electric light bulb with cord into the can. Turn on the bulb, and let the hub heat up for a few hours. At the same time, take the bearing, and put in in the freezer for a few hours. With the hub heated, and the bearing cooled, the bearing is much easier to tap into the hub. Note that the bearing installation must be done fairly quickly before the parts regain their normal temperatures and dimensions. Cheers, Glenn. PS be sure to use gloves when handling the hot hub!
Glenn

Thanks Dominic and Glen - very helpful advice. I may need to wait until after Christmas though, when there's space in the freezer!
Robert Sinclair

For Christmas I received a set of old BMC North American Service Bulletins that someone found at an auction(in a BMC binder and appearing to be completely unused). I thought that this one might have some relevance to this posting, particularly Item 6. I have never heard of such a fix before. I hope the formatting works.


NORTH AMERICAN SERVICE BULLETIN NO. 38
VOLUME 4
SUBJECT DATE
REAR AXLE HUB OIL SEALS. 11th December, 1957

TO ALL distributorS AND DEALERS:

Gentlemen,

When cases of oil leaks are reported from rear axle hubs, the following procedure should be followed:-

1. Ensure that the seal bearing surface on the axle housing is smooth and free of tool chatter marks.

2. Check the hub for running true on the axle. Eccentric hubs should be replaced.

3. Make sure that the axle breather is in operating condition so that no pressure build up at speed may occur.

4. Ensure that only S.A.E. 80 or 90 lubricant is used. Do not overfill the axle but rather fill to about 1/4' below the level of the filler plug.

5. Ensure that the spring tension of the oil seal is sufficient.

In cases where the above procedure has not proved satisfactory, and where continuous complaints have been received:-

6. Install an oil seal baffle between the hub bearing and the oil seal. The part numbers for each baffle applicable to the three series of axles are given below:-

"A" Series ... Part No. 2A.7293
"B" Series ... Part No. 1H.7077
"C" Series ... Part No. 1B.7525

Yours very truly


Peter Millard
General Service Manager,
North America

John DeWolf

I haven't heard of this baffle, but I can certainly understand the purpose and function. The bearing is milling around in a pocket of oil, and could tend to force oil past the seal if the seal is not in perfect condition. A baffle in between could shield the seal from the turbulence. A bearing with a built in single side shield could have the same effect, but I don't know if that would be available with this perticular.

Any chance there is a picture of this baffle in the Service Bulletin?
Barney Gaylord

Barney

In the back axle it is the other way round. The bearing is outboard of the seal and the source of the axle oil. Therefore it would not be "..milling around in a pocket of oil, and could tend to force oil past the seal.."

Steve
MG
Steve Gyles

Steve- The seal is still outboard of the bearing in terms of an oil leakage path. the path just doubles back around the axle casting.

Barney- there is no picture.
John DeWolf

Thanks John. I have just had a look at the cross section diagram in the Workshop Manual. I understand now. A new bit of knowledge everyday!

Steve
MG
Steve Gyles

Okay, the challenge is on. Anyone who can find a picture of 1H.7077 Baffle will be on my free beer list for next meeting.
Barney Gaylord

This thread was discussed between 14/12/2006 and 26/12/2006

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