Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Rear hubs and hub nuts

Hello fellow enthusiasts

I have plans to replace Oil seals, bearings, (O-rings) and paper gaskets on the rear axle. However, looking at my ’56 MGA’s rear hubs causes me a slight headache.

• It is my understanding that the outer bearing is lubricated via the half shafts.
• Furthermore, I assume that the outer O-ring is to create a (oil) seal between the hub and the splined-hub.
• Then, I read in Barney’s document RA-103: “Additionally, some of the very early production MGA 1500 cars had no provision for using the O-ring.”.

As you can see on the pictures, my hubs do not have a gland to accommodate an O-ring. Hence, I have an early 1500 MGA.

Therefore my question: What will keep the oil from running out between the hub and the splined-hub?

Also, does anybody have a good feel of which way the threads run on the right and left side (LH or RH) threads?

I thank you in advance for your thoughts.

Kind regards, Hans

Hansueli Ryser

I can't comment specifically on the A as I haven't yet has the need to play around with this area on mine yet, but the engineering looks very similar to sprites, which I am familiar with.

The sprite does have the advantage of an O ring as well as the paper gasket. Even so, leaks are not unusual, often occurring after taking the brake drum off as this tends to reduce the clamping action on the seals. If it does leak, it can contaminate brake linings. The answer is a good smear of your favourite sealing compound too.

The "big" nuts on the axle ends are more straightforward on the sprite as they are a reasonable size. THe only discussions have been about how tight they should be. I believe I read in one of barney's reports that they need to be bl**dy tight on the A in order to clamp the bearing and prevent creep. It seems to be a real so and so of a nut however! BTW, will a conventional socket which picks up the "corners" of a nut work? If so, what size?

On the sprites one nut is left hand thread and it is stamped "LH". If I recall correctly they are the opposite hand to the wire wheel nuts since the knock offs are handed one way as they rotate and the axle nuts the other as they don't! I appreciate that if the nuts are really tight, you don't know whether it won't undo because it's tight.... or you are turning it the wrong way.

Graeme Williams

Further comment on above ref handing of nuts.

I have found section H9 in the manual. This states that early cars did not have handed nuts.

"The left hand nut has a left handed thread introduced from car no 10917 (disk wheels) and no 11450 (wire wheels)"
Graeme Williams

(sorry, won't let me edit. so yet another post)

BUT if I am reading section H10 correctly, my interpretation suggests that the O ring was not fitted to very early cars ie only to those after axle numbers (is that the same as car numbers?) 5225 (wires) and 3725 (disk wheels).

As you have no o ring you must be a very early axle. Doesn't this suggest you also predate left handed nuts?
Graeme Williams


See my answer to your questions on the MGE Forum. Same as above re hand of nuts.

P. Tilbury

One potential issue with cars of the age of ours is that you can never be sure what has been replaced. It is possible that the axle casing may have been changed later in life and so although the hubs have no seal, the axle is of a later type. Are axle casing numbered on As? The ref to "axle no" in H10 and "car no" in H9 suggests they may be?
Graeme Williams

If you are really concerned about the lack of an o-ring, it may be possible to source a pair of later hubs that will have provision for it. Either way, it is probably a good idea to apply gasket sealer to both sides of the gasket, whether you have an o-ring or not.

There has been a lot of discussion about the correct o-rings to use in the past. The original style o-rings were of a square cross section, in a thickness that is no longer available. Current replacements are round cross section, and may not seal as good as original.

Back in the 50s, the addition of the o-ring was probably worthwhile. Today, our modern gasket sealing compounds are good enough that I doubt if the o-ring adds much utility, but most of us have the hubs that are grooved for the o-rings, so we have to fill that space with something.

One other issue I had, was that the gaskets I bought (from two different sources) were all too small, and the holes had to be trimmed slightly with a razor to get them to fit over the studs.

D Rawlins

Also, if you have one of the early axles with the RH threads on the LH side, be extra sure that you get the nut properly secured with the lock tab. I used new lock tabs just as a matter of course, but in this case I would for sure not mess around with trying to re-use them.

D Rawlins


Again, I thank you so much for your expert input.
Of course, I am a little shy of purchasing new hubs as it would set me back about $420.

Anyway, I also trust your comment that good sealer paste will do as good a job as the o-ring can do.

However, I am still a little concerned about the way the threads go because I have to apply so much force just to find out which way the nut comes off. Thus, trying to go the wrong way may cause some problems.

Thanks again Del

Graeme, I think you are right about the switch in the axle. The strange thing is that I have a 46" wide axle which means that it is a disc wheel axle. The ww axles were 44" in width. Anyway, the PO must have changed the "outside for wire wheels meaning that the car has splined hubs on it. So, it is a strange arrangement to say the least.

Thanks for you input!
Hansueli Ryser

Have a close look at the thread that is exposed with a magnifying glass and see if you can pick up whether it is LH or RH. I dont beleive there is any chance of stripping the nut if you tighten it a bit more in error - just try it both ways if you cannot pick up direction from thread examination.
Mike Ellsmore


I think this is exactly what I might do. Unfortunately, the nut is purfectly flush with the end of the axle and the threads.

Thanks for your input.
Hansueli Ryser

Dunno about expert... I'm just some guy that the gov't says is a mechanic, who has put together exactly one MGA rear axle assembly. But I'm glad if what I wrote was helpful.

D Rawlins

Let's ask the question of the other contributors:

"I know from Sprite practice that the Left Hand threaded nut is stamped LH. Is that the case for the MGA?"

If you have a steel wheel axle Hansueli and the conventional wire wheel set up with the correct half shafts, just check that there are no issues with the engagement of the spline half shafts into the diff. Again quoting my sprite experience I discovered that the slightly wider steel wheel axle that the po had used left the shafts short in the splines on the diff. There was only about 10mm engaged whereas the narrower wire wheel axle would have allowed another 15mm. I changed the axle pdq.
Graeme Williams

Graeme, thanks again for your input.
You know you are addressing the exact issue I am facing with my MGA. A MG-knowledgeable friend asked me what the width of the rear axle is from brake plate to brake plate. He pointed out that the original disc-wheel axle had a 46 inch axle whereas the wire-wheel axle is 44 inches.
My axle is 46 inches suggesting that it used to be a disc wheel axle. However, the ends are converted with splined-hubs to accept wire wheels.
So, bottom line is that I can't really say whether my rear banjo axle is original or not.
Because even the ww-conversions offered by Moss look different. Such that the rear splined hubs are mounted on top of the brake drums. Here, the splined hubs are mounted inside the drums. On the other hand, Moss' front conversion consists of new drums and 5-bolts splind hubs that mount inside these new drums. In my case, I have 4-bolt splined hubs that are mounted on top of the drums. As you can see, it is a little messy......
So in review, my wheel project began because I wanted to replace the 25 years+ old tires and as I removed the wire wheels I noticed that the splines were all worn on the hubs as well as on the wheels. After a couple of miss-orders, I finally have the correct new splined hubs identical to what I've had on the car.
Now, three of the four hubs do not turn easily forcing me to replace all bearings and seals.
This is where I am at now, trying to remove the rear hub nuts and trying to find an answer to the o-ring issue.
"Am I having fun yet.....?"
Hansueli Ryser

Hansueli, be very careful! If you have disc wheel axle case and WW half shafts, you will only have about 1/16" engagement of the splines at the diff. You need to get a WW axle case! I had the same issue by my PO doing it wrong. Fortunately I never drove it like that.
Art Pearse

Yes the nut is stamped And to get around the issue with the axles (which apparently have worked for years....) just don't press the axles so far into the hubs
dominic clancy

Art has definitely a strong point to be concerned about. On the other hand, Dominic is right too, this car has been on wire wheels for a long time.

@Dominic: What do you mean by "stamped nut"? The chisel marks?

Thanks for your thoughts
Hansueli Ryser

2" axle width is a lot - 1" less engagement on the halfshaft. But if it's run like that for years.....
You can get a feel for it as you push the half shaft home. If it's almost there before it engages in the diff then you could have issues.

Dominic: I tried your suggestion on the Sprite but it went like this:

Step 1: visited man with 10 tonne press to remove shaft from worn outer hub and fit to new.
Step 2: discovered when I put it back that little was engaged.
Step 3: visited press man again and requested shaft push out of hub by 1/2"
Step 4: tried to reassemble and discovered that the diameter of the splined end in the hub is larger than the shaft itself so, since this larger diameter was now protruding, it fouled the axle diameter.
Step 5: Visted man with press AGAIN. Got him to remove shaft, turn down the offending section at the end and reassemble.
Step 5: discovered thread for one of the nuts was distinctly dubious so replaced axle with correct one.
Step 6: asked man with press to push shaft back into hub by 1/2"

Ah to be wise after the event!
Graeme Williams

Look at the shaft ends and you can probably see witness marks showing the engagement, or as Graeme says, feel the engagement by hand.
Art Pearse

Moss can supply longer wire wheel half shafts for fitting to steel-wheel axles!
Graeme Williams

What a great thought Graeme. I quickly went out to the garage and too the half shaft with the old splined hub still attached and pushed it in however the base of the splined hub engaged with the four bolts coming from the hub before the half shaft engaged in the diff. So, I have to get the splined hubs separated from the half shaft first.

Would you know by any chance how long these longer wire wheel half shafts from Moss are?

@Art: Great thought as well :) I quickly checked it. There are light marks 25mm and 29mm alternating from spline to spline, measured from the end. See attached picture. So, I HOPE this is indeed how far the half shafts are engaging.
By the way, is that much engagement sufficient?

Again, many thanks you guys, you are awesome!!!!


Hansueli Ryser

Looks like you are OK!
Must have the longer shafts.
Art Pearse

Look at it the other way. If they were wrong and you changed axles they would engage by a further 25mm. Does the position of the markings indicate there is room for a further 25mm engagement?

I'm sure there will be something on MGAGuru listing standard lengths.
Graeme Williams

Graeme, I think it would have another 25mm or so to go.

As far as MGAGURU goes, I checked quite thoroughly I thought but couldn't find anything.

But do you think the 25mm as it currently is would be sufficient?
Hansueli Ryser

If there is no sign of distortion or wear and the car has been run "as is" then that would suggest it should be ok. But why not ask the question on this forum about the length of a w/w half shaft from the face of the spline hub to the free end. There must be someone with one available to measure!
At least you would then know whether it has been set up correctly.
Graeme Williams

Again, thanks Greame

I feel better now.

I must say, this forum is just amazing. I could almost work in real-time with all the advices I received.

Thank you ALL!!!!!!!!
Hansueli Ryser

Firstly the hub DOES take an O Ring. If you look at the photos I put on, you will see that there are different hubs available, but both use an O ring as can be seen from the parts manual. I would suggest that to use the steel wheel hub with a wire wheel mounting, you will need to get the O ring to stay in place in the hub, maybe with a little grease on the O ring to get it to stick.

The nuts with a LH thread are stamped with the letters LH, but on one side only. If the previous mechanic has mounted the nut with this on the inside, you won't know if it is LH or RH thread just from looking.

dominic clancy,2976621

For photos of the two hubs side by side
dominic clancy

I think, from another post elsewhere on this forum that Hanseuli has got the nuts undone Dominic.
Graeme Williams

Dominic, the 1500 and 1600 hubs were different as noted, and took slightly different size o-rings, BUT the very early 1500 hubs had NO provision for o-rings at all. This was not a change noted by car number, only by axle number. See Clausager page 70.

As noted at that other place, the early hubs could probably be machined to take the o-rings, but I think that would be a waste of time and money, given the improvements in gasket sealers over the past few decades.

Looked at the picture of the axle splines showing the light wear marks... I don't think the side gears are any wider than that, so that amount of engagement should be fine. It definitely doesn't look like an original shaft to me; there is some sort of dark coating, and all of the original shafts I've seen were plain, untreated steel.

D Rawlins

Thanks again for your kind support and suggestions. Yes, the nuts came off with the help of some words that I better don't repeat here :)
Also, I just tripple checked my hubs again however, they definitely do not have a groove to accommodate any type of o-ring. See close-up picture attached.

Now, I am on to reverse the work with new bearings and oil seals.

I wish everybody a very nice Mothersday-Sunday.


Hansueli Ryser

Are the witness marks on the halfshafts from this axle, or from their original wire-wheel axle?
Dave O'Neill 2

Dave, the witness marks are from the half shafts that I removed from the axle just days ago.

You know, at this point I am quite certain that the axle/hub/splined-hub combination is everything but original nor a common modification.

Here are the reasons why I think so based on what I understand today. Again, I have a 1956 MGA:
- I can't find the axle's serial number where it is supposed to be nor anywhere else on the axle
- my MGA is one of the very early MGAs (# 9631)
- my MGA has a 46 inch wide axle (from back-plate to back-plate) which indicates it is a disc axle yet, my car has wire wheels
- the half-shafts are long shafts as offered these days for ww conversion
- the hubs do not have an o-ring which seems to be in line with early MGAs yet, early MGAs are supposed to have R/H thread hub nuts however, the rear hub-nut on the left side on my car has L/H threads
- On the back, a common disc to ww conversion has the splined-hub mounted on top of the brake-drums. In my case the splined-hub is mounted inside the drums
- On the front, a common disc to ww conversion has the splined-hub inside the drums, in my case they are on top of the hub
- And, on the front, a common conversion uses a 6 bolt splined hub, in my case it has four bolts

I hope you can understand my confusion and why I have been asking all of you sooo many questions.

Anyway, I am sorry for being such a pain in the neck.

Do you think it is time for me to convert my MGA into a cool man-cave sofa?

Just kidding, I am eager to get my car on the road after it has been resting for decades in a barn.

Grabbing for air,
Hansueli Ryser

One other thing... I saw elsewhere that somebody recommended that you remove and clean out the axle vent. It's a good idea, but be careful. The vent fitting is easily damaged, and the available replacements are no good. Use big pliers and exercise caution not to break the skirt loose. Don't use a screwdriver. Usually that just results in chewing up the screw slot.

D Rawlins

Thank you Del. I will certainly check that also.

Would you know how best to clear the two drain holes that are located on the inside of the back-plates? I am not sure if I remember it correctly, but have you heard of using a 3/8" drill bit and use it (by hand) to clear the hole?
Hansueli Ryser

Del, may I ask, does the breather on the axle unscrew or do you just lift the cap?
Hansueli Ryser

The breather unscrews. I don't remember the exact hole size of the drain holes, but they are much smaller than 3/8". A small drill bit by hand should work, maybe even a piece of baling wire.

D Rawlins

Thanks Del for your input.

I took me a while to "unearth" the drain hole.... they were definitely not doing its job anymore. The hole size is about 1/8" to 1/4".
And, I twisted that dirty round hump on top of the axle....oh, that became the breather :) This breather was not only clogged but also covered with dirt, grease, ?

Well, perhaps this was another reason why the one hub, brake shoes, drum were so very oily...

Hansueli Ryser

This thread was discussed between 08/05/2015 and 16/05/2015

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.