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Gearbox Noise When Warm.


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#1 SolarB

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Posted 22 June 2016 - 03:55 PM

The Mini has developed a gearbox noise over the last few weeks. It's louder when the engine is warm and manifests itself as a low pitched whine when backing off the accelerator in 2nd, 3rd and 4th. It's present but much quieter when rolling in neutral. Under acceleration there's no noise.

Does anyone have a suggestion as to what it might be? I'll be pulling the engine out to repair the problem but it would be nice to have an idea as to what it might be.

 



#2 MrBounce

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Posted 22 June 2016 - 10:27 PM

You might find that your drop gears and/or their bearings might be getting worn out - although it could be other gearbox related issues.

#3 tiger99

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Posted 23 June 2016 - 04:08 PM

This could be several things. Doesn't seem to sound like drop gears, but not impossible. Maybe gearbox input to output shaft needle roller, or layshaft bearings. But if this is the main shaft output bearing, I recommend fixing it before further use, as when it goes it suddenly locks the front wheels, possibly at speed. You can guess how I know! It also ruins the final drive gears and maybe the casing. Symptom tends to appear on the overrun, a kind of whirring sound.

But it is all guessing, until you take it apart. If the gears are all good, a set of bearings and maybe synchro cones may be all that it needs.

#4 mk1leg

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Posted 23 June 2016 - 09:36 PM

what oil are you using all minis run on 20/50 mineral and nothing else.....



#5 SolarB

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Posted 24 June 2016 - 12:40 PM

Thanks for the input. I've been running the car on Millers oil, I forget which one but it's the oil for cars where the gearbox shares the engine oil.

I've been working on the car this morning and the engine is nearly ready to come out. I managed to fall off my mountain bike a couple of months ago and am a little limited on movement so my gallant wife is doing the difficult jobs while I supervise. Why didn't I think about this years ago? Having a willing assistant is wonderful.



#6 SolarB

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Posted 24 June 2016 - 03:49 PM

My lovely wife has pulled the engine out. We've stopped for the day but a quick inspection of the diff. output shafts shows an awful lot of radial play. None side to side, just radial. I have no experience of diffs. and have yet to do research, but is this normal?

 

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#7 Spider

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Posted 24 June 2016 - 09:22 PM

Your wife's awesome :proud:



#8 tiger99

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Posted 25 June 2016 - 08:53 PM

I was expecting to see your wife triumphantly holding the engine above her head. Perhaps just as well that she is not that strong!

 

And no, the play is not normal. It means that at least the bush in the diff side cover has failed, probably the ball or roller bearing too. Changing the bush requires reaming. You may be fortunate and find a good used side cover with bush intact. But do fit a new oil seal!

 

That is assuming the best possible scenario, only localised failure. But once the engine is off the gearbox, all will be visible.



#9 SolarB

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Posted 27 June 2016 - 06:11 PM

Moke Spider - have passed your comment onto my wife and she thanks you.

 

Tiger99 - I'm showing my ignorance here by not explaining properly. I'd removed the inner parts of the pot joints from the diff., hence the play in the splined shafts. I'd never realised the pot joints run in bushes which in this case look fine. I've removed the side covers and diff. casing and the crownwheel (?) and other components all look OK although I need to find the data to check clearances. I suspect the problem is in the gear box and will start stripping the engine tomorrow.



#10 Spider

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Posted 27 June 2016 - 09:43 PM

SolarB, if I can suggest, for the little money it costs, I'd be overhauling the diff as a matter of course while it's all out. I'd say the fibre thrusts have disappeared, but I'd suggest also replacing the Pin and Planet Gears too.

 

Cheers to your lovely wife mate :shades:



#11 MRA

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Posted 29 June 2016 - 10:33 AM

what oil are you using all minis run on 20/50 mineral and nothing else.....

 

Bite.....  10W40 is recommended by more tuners than not.






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