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MG MGB Technical - Are prop shafts prone to wear?


I could do with some assistance, I am rebuilding my 1971 mgb roadster, and have come to the prop shaft, but have no idea if mine is ok of not. Where do i look for wear? Is it worthwile replacing anyway?

Many thanks,
Alex Davies

Hi Alex,

The only parts of a prop shaft that can wear are the uni joints and the splines at the end going into the gearbox.
Of course damage could have happened, by a rock for instance, which would throw the shaft out of balance.

H J Adler

I'd take it to a propshaft place and have them check it out and balance it for you. I had that done to mine and it wasn't too expensive.
Simon Jansen

I second the suggestion by Simon above. Take it to a driveshaft place and have it checked over.

If any parts need replacing or the shaft needs balancing they can do it then and there.

Drive shafts normally last the life of the car and uni joints an sliding shafts will last for years with only even minimal maintenance.

Peter Thomas


I had my propshaft refurbished by a local company about three months ago. They replaced the Union joints at the front and rear, grease nipples, balanced and painted the shaft. I used to have some rattle and shake at motorway speeds but this is now gone. Really happy with the result and it cost less than a new shaft. I think the UJ are something which often gets neglected in servicing so I would advise you, like the others, to follow the same route.

P R Ives

As you know I have a GT and a roadster and have fitted new UJ's to both shafts myself taking care of course to assemble the shaft with the joints in the correct relationship to eachother. Both shafts are perfect at least up to 85mph and the cost of course was really pennies for the joints.
Iain MacKintosh

You've really got nothing to lose by fitting it and listening and feeling for any noises or vibrations.

For some reason both the Workshop Manual and Haynes set great store in marking the *flanges* so the prop-shaft can be reattached to the car in the original orientation. No harm it it for sure, but the prop-shaft itself is a balanced assembly i.e. it shouldn't matter how the flanges go back together, which is the case with a new prop-shaft. What's far more important is to get the halves of the yokes marked and reassembled as before, as that *is* part of balancing, and neither manual mentions this.

Haynes is also incorrect as it has an exploded diagram showing the yokes 90 degrees apart but an assembled drawing showing them in-line - they should be in-line, although this is only an issue if you part the sliding joint. And again, to maintain the balance the sliding joint must be reassembled *exactly* as it was before, 180 degrees out will give the correct yoke alignment but not the balance.
P Hunt

Further to Paul's comment, there are two stamped small arrows that show the correct orientation of the sliding splines - very hard to find but they ARE there!

FR Millmore

Thanks for that, as I've always said I'm still learning, and that is a case in point. I'll examine my old V8 shaft to see if can find them and take a picture for the section on my web site.
P Hunt

Fletcher,can you elaborate alittle for the "lay" folks(like me)..:)Thanks,Rich O
rich osterhout

I'll try.
One arrow is stamped on the female sliding sleeve, which is a machined forging and tends to be greasy. So the stamping is usually good and there's not much rust = good arrow. The other arrow is stamped into the main shaft TUBE = not the male spline shaft -, just beyond the weld. This is on the tube so it doesn't stamp well to start, and it gets rusty, all making for a mark you need to search for. There are two positions in which the UJ yokes can be lined up, so in an ironic reversal, we can use the orientation to help find the alignment marks! Find the arrow on the sleeve, line up the yokes and search for the shaft mark; you have two possibilities.

FR Millmore

Great job Fletcher,makes more sense (to me anyhow),Rich O
rich osterhout

Yes, those marks are quite small and faint from memory. My drive shaft is still all clean and nice. I can see if I can photograph them on it.
Simon Jansen

Simon,That would be nice
rich osterhout

Rich, will do when I feel up to facing the car again after my little setback! Am just having a break from car restoration for a week or so.

Simon Jansen

Annoying, scraped both parts of mine to shiny metal but no arrows.
P Hunt

You might well ask if they could spare it!
Don't know if they are always in this orientation to the nipple, think they may be.

FR Millmore

Took me 10 pics to get these two - reflections and flash are a bad combo!

FR Millmore

Those are arrows? I did notice a longitudinal 'scribe' mark on the shaft half of the yoke that looked as if it might have been deliberate, I'll have to have another look at the tube. My V8 shaft didn't have any nipples, which was why I replaced it (for one that has a nipple for the sliding joint as well as thr replaceable UJs) rather than just the UJs.
P Hunt

Looks like the stamp was flat and only marked half the symbol on the curved surface; I used to think the arrow was like a line with a flag on the end, until I saw one that had been double stamped and saw a complete arrow. The one pictured is unusual in that the stamp on the tube is better than that on the yoke.

FR Millmore

Fletcher,That was a wonderful job.I now understand the conversation in the above thread.Thanks for the pics,Rich O
rich osterhout

Looking again I can see what could be one half of the arrow head detached from the 'shaft', as it were (see pic), no 'flight' though, and it is off-centre to one arm of the yoke, not the space between the yokes.
Nothing visible on the tube in either orientation though, lost in the rusts of time.

P Hunt

This thread was discussed between 29/11/2009 and 05/12/2009

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