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MG Midget and Sprite Technical - Rear Axle

The time has come to remove the rear axle from my 1500 midget. It has a wire wheel conversion and there is too much play between the hub and wheel so these will need to be changed but also want to check the diff over and poly push the axle and also paint it while its off the car. My question is should I sandblast or simply strip with a wire brush and paint? I do not have sandblasting but am willing to spend the money to get it done right. Also thought about maybe powder coating it? Would this be an option?

I am aware I will need to buy 2 x new wire wheel and hub adapters is there anything else I should be looking a renewing while its off the car?
C Carter

you will have a nightmare getting all the blast media back out of the axle - even if you make nice covers for all the holes in it, media will still get in.
PeterJMoore

Thanks Peter that was my main worry think I will just go with the good old wire brush treat any rust then repaint.
C Carter

alternative plan: fully disassemble, sand blast, and then have a machine shop wash it in their caustic cleaning tank (like used for engine blocks after machining)

cleans out all the little nooks and crannies


Norm
Norm Kerr

I prefer a wire brush on the angle grinder followed by hammerite smooth.
Dave O'Neill2

You could have it soda blasted - that way after washing the only remnants left inside will be bits of rotten axle casing that came loose and it will not cause much of an issue as the soda will just get soaked into the oil, so a few oil changes and you will be back to full health
PeterJMoore

wire brush and then either chassis black enamel or Hammerite / Smoothrite. When you say 'wire wheel conversion' is it the correct axle casing or do your halfshafts only engage in the diff by half an inch or so?
David Smith

I believe I to be a conversion as the wire wheel hub seems to be placed on top of standard Hub and is held on with four bolts but now you have got me thinking. I will take a pic tomorrow as I am not sure now is there an easy way to tell.
C Carter

The "proper" wire wheel "extension" hub has a female spline in the centre to take the end of the half shaft. Steel wheels have a different half shaft with a large diameter boss at the outer end which bolts to the hub assembly. With wire wheels the outer end of the half shaft just has the spline and is a heavy drive fit into the hub extension.
The thing you need to be aware of is that the corresponding axle for wire wheels is about 1" narrower than the one intended for steel wheels. This allows for the potentially wider track that the wire wheel hub extension creates. Reducing the axle width brings the track back to "standard" and avoids the risk of the wire wheels fouling the inside of the wheel arch.
You can probably get away with a standard axle with the proper wire wheel hub units. In my case I had enough clearance between the tyre wall and wheel arch. However, the bit you don't see is more worrying. The wider axle is too wide for the half shafts so if the half shaft is fully engaged in the extension hub, the inner end at the diff is only just engaged (about 1/2"). As this is the end which usually fails I felt it was too risky and replaced my axle casing with the correct one.
I believe that the other option is to use the wire wheel kits which just adapt the steel wheel hub, half shafts and axle to take the wire wheel. It will have four bolt holes in the flange (but so does the original w/wheel extension hub) but as far as I'm aware it won't have the centre drive spline (no reason for it and expensive to machine if it isn't needed).
I think Peter May also makes longer "wire wheel" style half shafts to use with the steel wheel axle.

In my case, that lot was learned the hard way!
ps, if you decide to change the axle PLEASE don't ask about the torque on the thin nuts which hold the hub assembly on. Just email Lawrence direct!
Graeme W

chris i have some nice wires to get rid of
Mick - still wiring!!

Chris, photo should tell all. The other way is to measure between the backplates, or the handbrake rods are a giveaway too.
David Smith

Probably easier to measure the track and compared it to the infomration in the owner's handbook (what a useful document!)
G Williams

I will upload a picture and measure today. From looking at them again they have a welch plug in the middle of them and adapters that bolt on wouldnt need that would they? Thanks for the offer Mick but have been told that when replacing you need to buy new hubs and wheels otherwise they wear out quicker? Are you still on with your midget or is it still on its side in your garage?
C Carter

personally if there's a chance not to have and use wire wheels I'd jump at it, if the wire wheel conversions are just bolt on then unbolt them and sell them on with the wire wheels

I do however very much like that idea of looking in the Driver's Handbook for the information :)
Nigel Atkins

Ok just removed the axle off my car and pretty sure its a proper wire wheel axle. So looks like I need to remove the half shafts and buy some new ww hubs and get them pressed on. I could just swap the axle to a spare steel wheel one but wire wheels look better than alloy wheels. Has any one done this procedure. I have access to a garage press is this something I could do myself?
C Carter

to be sure if you measure the axle others here will confirm if it's a w/w axle, or look in the Archives as I've seen this subject covered

wire wheels may look good but them and their hubs cause more problems with use than non-w/w if you actually use the car regularly but each to their own
Nigel Atkins

I am aware of the issues with wire wheels hence this post lol. I do have a spare axle and minilits I can put on if replacing the wheels and hubs is going to cost a small fortune.
C Carter

sorry Chris I can't remember what other threads I've done let alone other BBSers and especially as you have a name sake here (Aquaboy)

I'm confused (nothing new) as to the type of conversion done but that photo and measurements would be good for others to confirm what axle you have
Nigel Atkins

Pic of the hub attached will take more tomorrow


C Carter

still on its side!
the wires are from moss and unused!
Mick - still wiring!!

yup, standard w/wheel hub and halfshaft arrangement. Could still be a steel wheel casing though - as you have a spare handy suggest you do a quick comparative measure to check.
David Smith

Still on its side you need to get it sorted Mick it has the potential to be amazing! How come you have got wire wheels? I am interested what would you be looking for?
C Carter

the wires are a friends and he got them when he was going to rebuild a 1500 he later scrapped! i'll ask him
Mick - still wiring!!

C: The halfshafts are a heavy drive into the hub extensions. It takes a press of around 10 tonnes to push them in. You then fit the welch plug at the outer end to stop oil leaks and if the shaft is fully home it's just short of the stop for the plug.
(Lawrence may be able to do this with an acro jack - see other post)

Warning: beware the cunning compromise of not pushing the half shaft fully home. This has an attraction if you have a standard axle because it means the hub/half shaft assembly is longer and so the engagement into the diff can be increased. If you do this the increased diameter around the spline at the hub end will foul the nut which holds the hub bearings on the axle! I missed this initially. You have to machine back the spline to get round this.

I had three increasing embarassing visits to a local machine shop while discovering the ins and outs of this process step by step. In the end I changed the axle and went back AGAIN to get them to push the half shaft back further into the hub extension again.
G Williams

I am going to clean up the axle today as its in a state and measure and compare with my steel wheel one just to be sure before I but the new splined hubs and take them to my local machine shop.
C Carter

THe other things that can get forgotten if you change axles are the handbrake rods. THey are shorter for the wire wheel axle. Nowadays the standard issues are adjustable but originals came in two lengths.
G Williams

Mick,

If Chris doesn't take you up on the wheels i may be interested , am just about to buy a set
cheers
Andy
Andy Chaffey

I have measured my axle and from backplate to backplate measures 41 3/4 " is that a wire wheel axle or standard?
C Carter

the backplate is not flat, what datum are you using? You said you had a spare steel wheel one too - how does it compare?
David Smith

If I am honest they look the same to me when side by side. I pulled one of the half shafts out and looks as though the hub hasn't been seated properly? Or is it correct?


C Carter

The Datum point was the flat on the backplate not the curved area.
C Carter

'If I am honest they look the same to me when side by side.'
I agree, that's why I suggested measuring them <sigh>.
My spares are either stood up on end or on high racking so my measuring was a bit imprecise but I see steel axle at 42" and w/w axle at 41". Measuring the handbrake rods (between hole centres) is another useful comparison.

Picking up on your latest post - it doesn't look right, possibly you have a steel wheel casing and the axle shafts have been extracted 3/8" either side to make up the difference?
David Smith

I will re measure tonight but it does look like a steel wheel casing. I will measure the handbrake rods too. Sorry I have been side tracked with work!
C Carter

Hub comment: looks like you are correct about not seated properly. I think that has been done to compensate for the fact that the assemby is being fitted into a steel wheel axle and therefore the halfshaft is too short.

Look carefully at the hub end - you will probably see that the half shaft has been reduced in diameter. To explain: the spline at the half shaft end is larger in diameter than the shaft itself. If you leave the shaft "half out" of the hub extension it fouls the big nut on the end of the casing as you pull the hub extension into position because the larger diameter spline won't fit inside the end of the axle casing.

If you change your casing to wire wheel you will need to push the half shaft "home" into the hub extension because if it is proud at the moment it will be too long to fit in the diff.

I'll get some measurements for you.
Graeme
G Williams

Can't get to the back axle to check without getting the car high enough to reach under so can't do that at the moment. However STEEL axle brake rods are (pin centre to centre) 26 3/8" and 14 3/4"
I got suspicious of mine when I checked the track width. You can compare that with the figure in the Driver's Handbook or Manual - you are looking for it to be about 1" too wide with the steel axle.

I went through all this lot in October and had decided to continue running wires on a steel axle. I decided that the half-seated halfshafts would be ok. But as I tightenned the large axle nut to a relatively low torque (and it isn't the oft-referred-to 140 ft lbs) the thread went. So went the whole hog and replaced the casing.

THe only other comment I would make is that my experiences are based on a 1275 Mk4 Sprite. I am assuming the 1500 is using the same parts!!

G Williams

yes 1500 uses the same parts except there are no handbrake rods to measure as it's a cable.
David Smith

My axle is not original to the car as it has rods not cables. I will measure them and post the results.
C Carter

Seem to remember only later 1500's had the cable only type ?

R.
richard boobier

The change to cable was '77 ISTR.
Dave O'Neill2

oh yeah, bugger - forgot that change point!
David Smith

Picture of the half shaft end that enters the diff. It looks quite worn to me with quite a deep groove? Are these going to be reusable?


C Carter

pic too blurred to tell - can you pan out a bit?
David Smith

That deep groove near the end, suggests the stronger halfshafts. It's not a wear groove, if that the one your talking about.
Lawrence Slater

It does look like it's only been engaging by about 1/2" though.
Dave O'Neill2

Have a look here:
http://www.healeyexperience.com/article/midget-rear-axle-knowledge.html

This lists information to check about wear limits on half shafts.


G Williams

Any conclusions on your axle, Chris?
G Williams

My conclusion is that I have a standard longer steel wheel axle. So I am at a bit of a cross roads as to where to go with this. I am thinking to press on new hubs onto the half shafts exactly the same amount as the old ones? It semms to have been like this for years and has been fine so dont see why it wont be again with the small mileage I do every year I dont think there will be a problem?
C Carter

"It semms to have been like this for years and has been fine so dont see why it wont be again with the small mileage I do every year I dont think there will be a problem?"

I was about say exactly that. Don't worry about it.
Lawrence Slater

I would have left mine if it had not been for the damaged thread. Remember it is the diff end of the half shafts which fail so compromise on the outer end, not the inner.
Don't forget to check the increase in diameter at the outer end of the half shaft. AS i said before, from my experience if you don't push it fully home into the hub extension (and you won't be pushing it home!) the increase in diameter of the half shaft protruding inside the hub extension will foul the end of the axle casing!
G Williams (Graeme)

<<Don't forget to check the increase in diameter at the outer end of the half shaft>>

That may well have been dealt with already, as it has presumably been running like this for some time.

If not, there could well be witness marks where it has been rubbing.
Dave O'Neill2

Ah Dave - yes you're right! I am accutely aware of this having to go back to the machine shop who pressed the half shaft into the hub and ask them to remove it, machine it down, and then put it back. Previously I had had to go back and ask them, having fitted it, to push it back out by 1/2". And then I changed the axle, so it was back AGAIN - "could you drive them back in again please!"
G Williams (Graeme)

This thread was discussed between 03/01/2013 and 17/01/2013

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.