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MG Midget and Sprite Technical - Vibrations again/still!

Hi. I hope you all had a good Christmas.
I took the midget down to Dorset for Christmas. A trip of 170 miles or so each with my new rear wheels and tyres, all nicely balanced and found that the vibration between 58 and 65 is still there and goes right up your spine to the back of your head. Not only that, the gearstick now vibrates at 75ish.
So the old buckled wheels where not the sole cause of the problem.
Just to recap, it is a 1275 MK3. All wheels (wires) have now been replaced as they were either buckled or the splines were worn. They have all been balanced using the correct technique by Brown and Gammons (front) and MGOC (rears).
The vibrations remain the same when the clutch is dipped and when it is taken out of gear and the clutch is released.
There is no stearing wheel wobble or vibration.

I have swapped the prop shaft for one I found on ebay - but they may both be unbalanced as far as I know.
If anything, the vibrations seem to be getting worse.
I think my next step is to eliminate the prop shaft completely by checking the balance. Does anyone know where I can get this done around the Herts/Essex boarder?
Then I will look at the diff. What should I be looking for?
What else should I look at?
Thanks for your help.
Dave
Dave Brown

Have you checked the tires themselves.They be out of round.
darnoc31

Dave,

As you have no steering wheel vibration that should rule out the front wheels. So their balance is O.K.

Might be worth changing front to rears just to rule out poor balance on the rears.(I've had poorly balanced wheels)

I used to have to get wires balance on the car to get them 100%. Only got rostyles on the current car.

Did you say the raer tyres are new ?

R.


richard boobier

Richard,
Rears are new and balanced as are the fronts, but it may be worth swapping withe fronts just to see if it makes any difference.
Dave Brown

Dave, one thing that I experienced a long time ago due to hitting a kerb was not only buckled wheels but bent stub axle/drive flange... Took me a whle to go thorugh tyre/wheels before it became the only thing left.- sure enough a new flange sorted it out.. was on a fwd car ( princess !)

from what you say it doesn't spnd like front end - if you have absolutely no wobble/judder on the steering - then points to rear end.

have you had the Toe in checked when you refitted the new wheels. ( I think that would give wobble on steering if it were wrong)

assuming it rear end - then prop and maybe loose susension mounts is the only other items I can suggest.

Flanges can be checked with a dial test gauge on a firm base ! and spin the flange over...

let us know what it turns out to be...

Gear stick tizz is probably just the anti rattle spring/seat worn out...
John Barber

could it be wheel hubs, brakes(?), engine, gearbox

gear lever rattle could just be the need for an Anti rattler kit - Gear lever QTK5: £3.53 (inc VAT)

which would I’d imagine consist of:-
'O' Ring TRS710: 31p (inc VAT)
Button 2A3467: £2.40 (inc VAT)
Spring 2A3390: 77p (inc VAT)
(5p cheaper!)

ETA: John beat me to it whilst I was finding part numbers
Nigel Atkins

Dave,

My suspicion would be the prop shaft UJ's. Both on the original and on the e-bay replacement. It would be bad luck I know, but it is such a common fault anyway that it increases the likelihood that the replacement was also faulty. Even if the replacement one was supplied as "fitted with new bearings" it is possible that one or more yolks was inadvertently reversed.

I think you have tried / eliminated most other possibilities anyway haven't you? ;-)
Guy

Oh, I forgot to say, I replaced the button, spring and O ring.
Dave
Dave Brown

Dave,

Could try jacking up the rear (Handbrake off - fronts chocked) and check for movement in the rear hubs by racking the wheels side to side )loose wheel bearing - never had this myself but you seem to have tried everything !

Also the diff flange - check square as it turns (no runout) and no play up/down.

Unlikely to be two propshaft problems - (assuming u/j's are not shot).

Did the gearbox output shaft bearing have excessive play when you fitted the prop ?

Running out of ideas !

R.
richard boobier

Guy beat me to it - slow typist !

R.
richard boobier

that only leaves plate/cover/screws might have come loose then :) well as far as anti-rattle kit anyway

good points on not relying on or discount parts being correct or fully working just because they are new or replacements

just reread your OP, probably be able to discount engine and gearbox then :)
Nigel Atkins

Hi Richard,
I didn't check the gearbox output shaft bearing. I managed to fit the propshaft with the gearbox in place!
Guy,
The ebay prop shaft was second hand with no history but no play in the UJs (Does not mean that it was balanced though). The original one had the UJs rebuilt and I think I got the yokes back in the correct place. I did notice a blob of weld on a crack on one of the yokes, I assume from a previous rebuild when a bearing cup could not be removed. That, and the vibration, is why I replaced it.
I guess I will have to check its balance.
Dave
Dave Brown

Dave,
I have had worn UJ on propshafts that still felt quite tight with no apparent slack. But on dismantling the needles in the bearing caps were all mangled up causing vibration. So it could still be that.

Sorry, I missed your original key question - as have others! Any engineering shop should be able to check the prop shaft for balance in just a few minutes. These specialist at Luton shouldn't be too far from you though:
http://www.reco-prop.co.uk/services

Guy
Guy

Guy,
I have just spoken to the MGOC technical guy. He recommended reco prop too. I will be going along there soon.
He has also suggested swapping wheels front and back just to 'tick the box'.
I need to get two rear hubs soon so I will be checking the half shafts and rear bearings at the same time.
The next step is to eliminate the diff by reconditioning. If that does not do it, I will have to look at the gearbox.
It could be an expensive new year!
Dave Brown

Good advice, but from your earlier discussions on this I thought you had already tried swapping wheels and tyres around, using your spare.
Guy

Dave,

I could loan you a 3.9 diff if you decide you need one to try.
Have to sort transport somehow unless you are down this way.
I'd have thought if it was that it would be easy to spot when out.

I'm still thinking wheel balance/propshaft.

R.

richard boobier

Thanks Richard,
I was down that sort of way over Christmas - Beaminster in Dorset, but back at home now. I was going to post last week while down there, I wish I had now.
Still thanks for the offer, I will swap the wheels over at the week end and then get the prop shaft looked at. I hope that will sort it.
If it doesn't then I may take you up on your offer.
Thanks
Dave
Dave Brown

I wonder if another possibility might be a damaged half shaft?
Guy

Hi,
An update on the vibrations.
I have just swapped the wheels front to rear, rear to front and put the original prop shaft back (with a blob of weld one one of the yoke where it has been cut to remove a circlip I think) and the vibrtation has all but gone.
I think that the old rear wheels where a problem and the new (second hand from Ebay) prop shaft also has a problem.
As all the yokes on the new prop shaft are sound, I will get that one reconditioned and balanced by reco prop and fit that back on and I hope that will remove the slight vibration.
Dave
Dave Brown

This thread was discussed between 29/12/2011 and 03/01/2012

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