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MG MGA - Hub splines

I'm getting a metallic click from the rear hubs most times I reverse drive. there is a 3/16" rotational play at the tire tread with the handbrake on and the spinner snugged but not tight.
Please examine the pics of the splines attached and give me your expert advice. I want to order new WW but don't really want to change the hubs as well unless I have to.



Art Pearse

And here is the wheel splines.
I suppose I could always buy the new wheels then check for play first.
How much is acceptable?



Art Pearse

Hub splines look good to me, wheel splines look worn. Do you have a friend with new wheels to trial fit?
Mike Ellsmore

Agree with Mike- try a new wheel first--
But the taper on the hub looks a bit worn as you can see where the ends of the wheel splines have got into the surface of the taper----If yo put a new wheel on there it won't seat properly, really the hubs need a trip in a lathe(after confirming the splines are ok)and the taper dressing true-
It's a bit of a result of worn wheel or hub splines and/or wheels not tightened up enough

Also the noise could possibly be coming from the spline where the drive shaft fits into the hub--something to check if you end up pulling the hubs off

willy
William Revit

I agree with William that once the wheel splines begin to mark the taper on the hub you will have this problem of the wheel not locating properly and it cannot be correctly located and tightened.
However, I disagree that it is caused by wheels not being tightened enough. The taper on the wheel is in fairly light material and the taper is easily spread in diameter by the much harder hub taper if over tightened.
You then get the problem that you have so you tighten the spinner more and make the problem worse.
As mentioned it would be best to to try a good wheel first. But do not over tighten !

Mick
M F Anderson

I have attached an image of a severely over tightened wire wheel.
The pitch of the spinner thread gives a vey high mechanical advantage when being tightened. This spreads the diameter of the taper on the lighter metal of the wheel compared to the harder metal of the taper on the hub.
A loose spinner will damage the splines but it will not cause the wheel splines to be forced against the hub taper.
Spinners are self tightening. I normally gave them two light taps to ensure they are seated then one moderate hit only.
After a few laps on the race track they needed heavy hits to remove them.

Mick



M F Anderson

I believe if my dad had replaced the hubs when he replaced the wire wheels back in the mid 80s, I would not have needed to replace either of them, but instead I have had to replace both. They wear as a set, and I think if you are replacing one half of the set due to wear (as opposed to damage, such as a bent rim), then it is best to replace both wearing parts at the same time. Otherwise you risk having to do it again later.

-Del
D Rawlins

I have cleaned these indents on the hub up with Dremel grinding wheel without damaging the taper. Mike
Mike Ellsmore

Hi Mike,

Yes, grinding away the indentations on the hub will allow the taper of the wheel to move forward and again contact the taper on the hub.
This may solve Art's problem and save a lot of money.
It must be remembered that doing this more than once will keep moving the wheel forward and reducing the length of the meshing length of the splines.

Mick.
M F Anderson

Mick, Mike and Willy - I see the marks at the foot of the taper. I guess the point is that in this area some metal has been raised above the taper line? So dressing this area with emery etc will fix it?
The wheel is actually quite a sloppy fit, and I only know which wheel was on which hub for the last 6000 miles. Before that , no idea!
Art Pearse

Willy, your remark about the internal hub splines (to the driveshaft) - I thought this was a very tight press fit, so is it a real possibility to be loose?
Art Pearse

Art: I had a halfshaft which had movement within the outer spline hub on a Sprite. It could move up and down by about 3mm before it went tight. I have no idea how it cam to be like that. When I needed to replace the outer hub on the other size it was a 10tonne press job to get the shaft out.

Standard advice is to replace both wheel and outer hub as not doing so will just mean that the retained item will rapidly wear the new one. Easily said and then you look at the cost and start to think......
Graeme Williams

Yeah, changing the rear hubs is a bit of a pain but it's not the worst thing, either. Art's hub looks pretty worn to me... The peaks shouldn't be getting thin like they appear to be; there should be a definite flat on the top of each spline. If you don't have a press it is fairly standard shop work that you should be able to get done easily enough. The hardest part is getting the expansion plug out of the old hub. Best way I have found to do that is tack weld a long bolt to it using a MIG unit and then it will usually lose its grip and pull right out.

-Del
D Rawlins

Art
Yep press fit but I went to replace some splined hubs on an early B once,first one was a very tight press fit and second one was like Grahams' with a loose spot and then went tight and needed pressing but less tight
Axle splines were ok and pressed equally into the new hubs and gave no trouble afterwards
William Revit

My advice would be to measure the hubs. Actually I do mine every couple years. It's best to use vernier caliper to measure the hubs:

New part: 2.450 "
Good part: 2.440 "
Operative: 2.430 "
Borderline: 2.425 "
Dangerous: 2.410 "

I recommend taking the average of four measurements on each hub as you can sometimes find flat spots.
D Quinn

This is the O.D. of the hub splines?
Art
Art Pearse

D. Quinn, thanks for the standards.
So, I find my front hubs are in the new to good range but my rears are in the borderline and dangerous region. LR is 2.390 !
So, its new rear hubs for me. The fronts were different source than the rears, but I imagine rears wear more rapidly.
Art Pearse

Art, you are welcome. The LR is clearly in the dangerous zone.
D Quinn

Just got new rear hubs from Moss. OD is 2.430
My old ones have coarse threads, the new ones are fine, 12 tpi.
I'm thinking the PO used MGB hubs, so I'm hoping that's the only difference, the thread. So, new spinners too.

Art Pearse

Any ideas on why my rear WW hubs have coarse threads?
Art
Art Pearse

What is your axle ratio? If somebody swapped in the 3.9 center section out of an MGB, they may have also installed the MGB shafts at the same time. This would have saved them the trouble of swapping out the side gears in the differential to match the MGA shafts, at the cost of then having to use different knock offs than on the front.

-Del
D Rawlins

Art,

Those rear wire wheel hubs w/coarse threads, if they come with the MGB diff, may have stud holes for the MGB (1/2"studs). You'd better check your new hubs. If you ordered the fine thread WW hubs for your MGA axles the stud holes will be for 7/16" studs and therefore will be a bear to install.

I just did this op. and fortunately discovered the stud difference when I tried to use the MGB brake drums on my MGA hubs - WAY too loose!

Good luck,
John
JR Alexander

Del, it's 4.3, so it is an MGA diff. It came to me in a disc wheel casing, fortunately it had not been driven as there was only about 1/16" engagement at the diff. I got a WW casing and swapped it out.
John, I will check the drums on the new hub first. Thanks
Art
Art Pearse

John Alexander - I checked the studs on my rear hubs and they are 7/16, and fit the holes on my new MGA hubs. The stud pitch is also the same.
So, I am wondering if the only difference between the new MGA hubs and the old hubs on my car is the thread pitch for the spinners?
I have already checked the diff ratio (4.3) a long while back, so it is MGA.
So I'm thinking all I have to do is get the shafts pressed out the old and into the new hubs, unless there is a difference in the fit to the bearing carrier. It has the big R&M roller bearings, which I think is also MGA.
Incidentally, I tried the new hub fit in the old wheel and it feels really good, no play I can detect by hand.
Art
Art Pearse

Art,

Looks like you are good to go when you get the new 12 tpi spinners and press the new hubs onto the half-shafts. Before pushing the half-shafts out of the old splined hubs, be sure to measure the distance from the diff. end of the half-shaft to the hub side of the spline hub flange so, when pressing the half-shaft in, it won't be pressed in too far which makes for a shorter axle.

Don't forget to purchase a new expansion plug for each axle hub. When installing the expansion plugs, paint a little Permatex 3H (semi-hardening goop) around the perimeter of the plug to prevent later oil seepage. If it works on aircraft applications it'll work on these old Brits.

If nothing else, I think these marvels of modern engineering tend to make us all a little better at problem solving.

Carry on,
John
JR Alexander

Thanks John. I've also asked the same question to Moss, before I start the work, but its looking good. I'm very aware of the shaft lengths as the same PO put them in a disc wheel axle, with only about 1/16" engagement at the diff! Fortunately he never drove it like that and I swapped the case. Is there not a hard stop on the hub splines when pressing?
Art
Art Pearse

OK, next question - how do you remove the old expansion plugs?
Art Pearse

There is no hard stop. Splines go all the way through the hub, with a counter-bored shoulder in the outboard end to accept a Welsh plug. The shaft needs to be pressed in to be very close to the shoulder, may even be flush with the shoulder (but not past the shoulder). If the shaft pressing stops as much as 1/8-inch shy of the shoulder the half-shaft may bottom out on the differential pinion shaft before seating the gasket at the outboard flange.
barneymg

to get the welch plug out drill a hole in the centre of it and use a self tapping screw to wind it out, or grip the screw with a plier and pull the plug out
Dominic Clancy

ok, thanks Dominic and Barney
Art Pearse

OK, still a problem. The old hub extends a bit more than 1/4" through the wheel hub. The new hub only comes flush, despite the dimension from the start of the taper to the end of the threads being essentially the same. I can get a start on the threads and go 4 turns until it gets firm. If I feel at the back I can feel that the taper seat is not fully seated. I'm at a loss to see what is holding it up. I'm attaching some photos and a drawing with dimensions of both.
On the ne hub, the land btw the flange and taper is less on the new hub. I hope it is enough to clear the drum nuts.
I have not tried to force the hub in further using the spinner, just hand tight.



Art Pearse

Dimensions


Art Pearse

Old hub threads pic


Art Pearse

Art,
This is what I observed when I dismantled an early MGB rear end to get the 3.9 diff. and axle shafts.
The flange to taper dimension (MGB) was about 1" as is your old unit. The new hub is as yours is (.75").
When I got the new hubs I, too, wondered. Took off one of my MGA's rear wire wheels and found the hub also has the .75" dimension.
There is something holding up the full seating of the WW to your new hub but don't worry about the drum nuts interfering with the wheel seating fully.
My new hub threads extend about .25" beyond the wheel as in your "Old hub threads pic".
I wire brushed the old grease out of the splines in the wheels and applied fresh and they slipped onto the new hubs with firm pressure.
JR Alexander

Thanks JR.
I need to check also the shaft extension from the hub flange. The A and B shafts are the same (453-350), but the shorter land on the new hub might cause a greater extension, unless the seating position is different. One more measurement - from hub outer to inside where the shaft ends.
Art Pearse

Looks OK. The shaft in the B hub sits about .35" deeper from the outside.
Art Pearse

OK, hub fit the wheel with a bit of friendly persuasion. Nice tight fit.
Now off to machine shop for the pressing.
Art Pearse

This thread was discussed between 05/08/2017 and 31/10/2017

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