Morris Minor Owners Club

Apologies inadvance for the long windedness of this.
My 64 van suffers from really bad propshaft vibration. I say its the prop as you feel it through the floor as it comes in at about 50. If you hang on tight and keep going it smooths out again at about 70ish, but by that time you've really had enough of driving it!
Steering is relatively smooth, as is the gear lever. I've had different sets of wheels and tyres on it, both crossply and radials and its still the same when in neutral and coasting, which is why I thought it was the propshaft. I fitted a good spare, which was still the same, then one I'd fitted new UJs to - no better, and this week borrowed the one from my convertible, which was known to be ok, and its still bad.
I'm now getting the feeling that the propshaft may be ok and its something else
Now, about this time in 2006, I had the diff seize up. Own fault, it had been whining for ages, then the pinion bearing broke up whilst going past Manchester Airport, locking everything up solid. I skidded to halt on the hard shoulder, (after leaving the longest skid marks I've ever seen), and got recovered home. It was winched onto the transporter and I had to drag it off with the Land Rover when I got back. The diff was wrecked and the halfshafts were twisted, as the rear wheels had tried to continue going round. Anyway, I did a quick repair and replaced the diff and halfshafts and got it on the road again. Day to day running about, I rarely get onto a big enough road to get up to 50, so the problem didnt arrive or wasn't noticed for sometime. Only really noticed it when heading north for the JOGLE run in June 2006.

I'm now wondering if the diff locking up incident may have bent the axle casing and is causing the vibration.
Anyone any theories or ideas before I pull it apart and swap the axle?


Parked at a funny angle on the hardshoulder after skidding for ages

My thought is you might have twisted or bent the mounts on the differential casing for the leaf springs.

I had similar symptons coming in at around 50mph but too severe to 'drive through it'. The fault was that the pinion flange to which the propshaft bolts was bent and running out of true. Chock the car safely and watch the prop rotating, it will soon be obvious if the flange is out of true. Fortunately, it is easy to change the pinion flange and you merely have to tighten it up to 140 ft lbs afterwards.( The amount of running out of true was not great but enough to make the car undriveable at 50).

I had the pinion flange work loose - a standard 1098 engine doesn't produce 140ft lb of torque so I guess it wasn't tight enough in the first place. That gave a lot of vibration at 50mph when not under load so it was OK going up hills but I had to go down hills more slowly. I'd imagine that sloppy UJ's would give the same symptoms.

I've a spare axle if you need one.

if the locking up was severe enough to do all that damage then I would also say that the pinion flange is also out of true.

Stupid suggestion / question perhaps but are props balanced? If so could th weight have gone for a burton - same maybe applicable to the wheels?
Sounds like a very specific range for it to be occuring...

Diff may be running at an angle if the axle spring locations have been twisted (mentioned above) or just rusted. For prop shaft to work correctly the two ends must be parallel to each other - so if gearbox is parallel to the road, so must be the diff input shaft. Could also be the gearbox output shaft bearing or less likely - the gearbox mountings. You've tried so many prop shaft options - it can't be that!

How long have you had the car? Has it always done it? Are the tyres and wheels the same size? Sounds daft, but I've seen some very similar looking 13" and 14" wheels.

I groaned when I read this, I have posted the same question on here before having identical symptoms with our 65 convertible. I have replaced:
- gearbox with refurb unit, no difference
- propshaft UJ's, made it a lot worse, vibro started at 35!
- balanced propshaft, no change
- replaced propshaft with a good s/h unit, much better and bearable but still there
- replaced diff with good s/h unit, got rid of the whining but not vibro
- o/s hanger replaced, no difference
- both rear shockers, no difference
- straightenened and balanced wheels professionally, no difference
- all tyres are correct size and checked as not warped
- both rear springs, no difference
- all poly bushes and new shackle pins
- renewed both rear wheel bearings, brake drums and linings
- replaced axle shafts with NOS ones
- considered replacing the rear axle casing but ran out of steam

I contacted previous owners, none had experienced the problem.

Consolation - the ride is very smooth now and we rarely drive over 50 anyway, I will try again in the summer to sort it.

IaininTenbury
As you've changed wheels and tyres, and changed the prop, then first thing I'd try is a known good diff. It may even be worthwhile to change the entire axle - later axles are not too hard to come by, and although it takes longer than changing the diff, it would rule out anything to do with the axle.

To state something else (that you may have already checked is the gearbox...) The prop runs in a plain bush. If the bush is worn then the prop can run out. I've had this happen. Normally this will be evident by vibrations in the gear lever, however it's not easy to tell the difference between normal vibes and the extra ones from a prop runout.
As you didn't have the bad vibes before the diff seized, then it's unlikely to be anything more sinister in the gearbox - however I'v had one with a bent output shaft! I rebuilt the box with new bearings and bushes only to find the same vibes 100 miles later (when the bushes freed up) I was amazed that I didn't spot the bent shaft the first time round, but I'd not been looking for problems.

I replaced the box, but in that time, the replacement prop had worn the nose due to run out on the dodgy gearbox - so it also ran out on the new gearbox.

3 gearboxes, 2 props and 4 engine back plates later, I got rid of the vibes. However I tend to get a cold sweat if i see a figure-8 shape in the rear view mirror (the car behind's headlights made a fig-8 shape in the interior mirror when I was getting the vibes)

Thanks for all the suggestions. Looks like I'm not alone with this problem
The latest propswap for a known good one off my convertible was a desperate move really, being an easy thing to change, And I've had various sets of tyres on over the last two years from a nearly new set of Michelins, to Town and Country crossplies for running around in winter on. None of them cured it, the T&Cs being marginally worse, though not unexpected really.
My theory about axle damage occured about halfway down the motorway from the Manchester Bus Museum Rally, whilst trying to find a speed that didn't make the rear view mirror droop with the vibration, so I've not had chance to inspect the spring mounts on the axle yet. The diff was replaced in its entirety after the old destroyed itself, though the 'new' one was just one lying about so it may conceivably have a problem. I didn't think it was the gearbox end as the lever dosen't vibrate too much - certainly not in the same way as the big vibration. It is slightly worse on the overun, so after achieving warp speed there's the sickening feeling that its going to be a whole lot worse slowing down again....
I'll get it jacked up tomorrow and have a good look.

IaininTenbury wrote:It is slightly worse on the overun, so after achieving warp speed there's the sickening feeling that its going to be a whole lot worse slowing down again....

The frozen diff would tend to twist the axle forward in the same direction that overrun does, which supports the theory that the axle mountings or even the axle casing could be twisted in some way.

Update!
Tried jacking it up today and running it. The diff flange was obvious not running true, hence the back end of the prop was also waving about. I've never tried this with a good Minor, but assume that 4-5mm out of true is quite probably the cause. With the engine off, I stood an axle stand next to and in contact with the diff flange. When rotated a 4-5mm gap opened up. Theres no play on the input flange, it just looks like its bent almost.
Anyway, looks like I'll be trying another diff first. Axle casing looks ok from what I can see - (Its pretty muddy round the spring mounts and the sort of gusty day that blew any disturbed grot straight in my eyes...)

but assume that 4-5mm out of true is quite probably the cause.

Bloomin' eck! there's your problem. I'm amazed the back end didn't destroy itself with the G forces. New diff should cure it, but check the prop shaft UJ's, especially the rear one, all that run out may have done some damage to the needle rollers or cages.

Good result, it is very easy to fit another pinion flange without changing the diff. That amount of out of true is HUGE.

But of course the damage/out-of-true may not just be the diff flange - but it's certainly worth a punt!

see post no five

The original diff that seized went in a skip, but the replacement was just the first 4.22 that I found on the shelf so no idea of its history. Tomorrow is the day for sorting it - been dashing all over the country over the last few days and not had time. If I had, I'd have took it to Brooklands today even if it meant starting from York where I was this am...
As it was, I had to use a modern car, which I shall not mention!

Well, I took the plunge today in a spot of nice sunny weather and pulled it apart... Had the diff in the vice with a piece of welding rod clamped to it and measured the run out. At least 3mm and quite obvious. Not sure its its just the flange or the whole pinion shaft thats waving about. I'd guess its probably been dropped in a previous life as I cant see otherwise how that would occur.
Anyway, I fitted another diff (4.55 as I couldn't find a 4.22 in the spares stash so it scoots up hills nicely) and its transformed! Have to keep looking at the speedo now rather than just feeling the speed!

An interesting side effect of the strip down, was that I noticed one of the hubs was loose - that is the bearing was loose in the hub and the hub could be pulled in and out about 1/4". On close inspection the other side was identical.
It passed the MOT a couple of months back as there was no play when rocked , but the tester never tests for in and out movement... I tried a new bearing, but that was a sliding fit int he hub too so I fitted two s/h hubs off another axle.
The result is that the slightly wobbly handling, that I'd put down to having town and country crossplies on the back has now gone and it handles quite nicely. So a double result!
Was like driving a new van when I came home this eve!
Thanks to all of you for the advice

As an aside, could someone define 'run out' for me? I've often wondered just what it meant
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...and yes, open to 'jokes', I know - in the context of the above...