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Vibration under load

Old 09-11-2018, 07:12 AM
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Default Vibration under load

I know this has been covered a fair bit, and in part by me! But its worth another shot before I start re mortgaging the house..

For much of my S2000 ownership, I've been plagued to a greater or lesser extent by a vibration under acceleration. I've swapped the drive shaft cups around (and learnt they weren't bad anyway) I've replaced wheels, I've replaced knackered/split diff mounts. And I've still got a problem. Which, following a heavy stint at the 'ring, is quite bad.

The symtoms are these..
Under heavy acceleration, the car shakes quite violently. Its worse when going up hill or accelerating from lower in the rev range; when asking more of torque. If just maintaining a constant speed, its fine. Similarly its fine if you know it out of gear. Its only when underload. And perhaps as you'd expect, its worse it acceleration hard. More gentle in-gear acceleration causes a more gentle version of the same.

What should I check??

I've started thinking its likely to be driveshaft (out of balance?) or prop shaft related. Any input? I've given to understand the these are not cheap so I don't want to replace on a whim.

Would tired engine/gear box mounts give these symptoms??

Thanks
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Old 09-11-2018, 10:21 AM
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Anyone near you to try swopping propshafts? Is the car pulling fine under power, could a misfire cause a vibration?
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Old 09-12-2018, 12:53 AM
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Well there is an S2000 owner a mile or so down the road from me. I've never spoken to him/her though, and I cant imagine they'll welcome the suggestion I pull their car to bits. Perhaps worth an ask though..

Anyone able to tell me what is involved in prop shaft removal?? Too much to hope its just 6 bolts at each end and away you go I suspect..? I once helped a friend remove the prop shaft on his old M5, and beyond incredibly tight bolts, I don't recall it being too much agro.

And yes its pulling fine in terms of making and laying down power, just shakes the cabin to bits in the process
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Old 09-12-2018, 01:09 AM
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Originally Posted by S2Bray View Post
Anyone able to tell me what is involved in prop shaft removal?? Too much to hope its just 6 bolts at each end and away you go I suspect..?
IIRC yes thats all but use threadlock when re-applying, some people have had the bolts seize. Shock em first and clean the bare ends is my advise.

Also with regards the engine mounts you should be able to see the tops of them with a mirror and some acrobatics, if theres a crack on top its worth replacing. Gearbox mounts are easy enough to do as well, cheap too IIRC.
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Old 09-12-2018, 02:15 AM
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Originally Posted by Irish TuneR View Post
IIRC yes thats all but use threadlock when re-applying, some people have had the bolts seize. Shock em first and clean the bare ends is my advise.

Also with regards the engine mounts you should be able to see the tops of them with a mirror and some acrobatics, if theres a crack on top its worth replacing. Gearbox mounts are easy enough to do as well, cheap too IIRC.
Cool, cheers.

By "shock them", what do you mean?
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Old 09-12-2018, 02:50 AM
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Have you tried jacking car and spinning in gear,for a visual ?
with great care !!!!
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Old 09-12-2018, 02:59 AM
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Is the vibration at engine speed or car speed?
If it's the engine/gearbox mounts I'd expect the vibration to occur at certain engine revs regardless of which gear you're in or speed you're travelling.
If the problem is in the drive train after the gearbox ie prop shaft, drive shafts, diff mounts, rear suspension, then I'd expect the vibration to occur at certain speeds.
Can you put it on a rolling road and get more indication of where it's coming from?
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Old 09-12-2018, 03:35 AM
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Originally Posted by noodels View Post
Have you tried jacking car and spinning in gear,for a visual ?
with great care !!!!
I happy to do this, but I don't really know what I'm looking for, or what is or isn't normal in those conditions.
That said - I did recently grip the propshaft and try to turn it in my hand when it was last on stands, and I was able to rotate it back and forth freely maybe 5 or 10 degrees without it having any affect on rear axles. I assumed this was normal...
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Old 09-12-2018, 03:39 AM
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Originally Posted by devon2k View Post
Is the vibration at engine speed or car speed?
If it's the engine/gearbox mounts I'd expect the vibration to occur at certain engine revs regardless of which gear you're in or speed you're travelling.
If the problem is in the drive train after the gearbox ie prop shaft, drive shafts, diff mounts, rear suspension, then I'd expect the vibration to occur at certain speeds.
Can you put it on a rolling road and get more indication of where it's coming from?
The vibration occurs in all gears, at all speeds. Any gear/any speed can be rendered vibration free by not accelerating, but under load it vibrates. Under half throttle, it vibrates a bit. Under full throttle, it vibrates a lot. Its pretty consistent in that respect.

I don't have ready access to a rolling road, but I guess I could find one...

EDIT: perhaps that isn't entirely accurate...Under full throttle the vibration is more subtle at lower rpms, coming on stronger from 4000rpm, and then really quite shouty at 8000

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Old 09-12-2018, 05:17 AM
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I see you have already done your drive shaft cups swap. Is there a noise associated with the vibrations? Wheels bearing or could be diff related. The prop has a little movement on it, so should damp vibrations from the engine.

You can check engine mounts etc from this post: https://www.s2ki.com/forums/s2000-un.../#post23032920

Does the engine idle ok?
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