darrens
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| posted on 23/3/08 at 02:52 PM |
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Odd Vibration
Woundering if someone could possibly shed any light on an odd vibration the car has everynow and again.
This only happens (intermittently) when the car is pushed hard accelerating or hard decelerating on the engine, something either on the
engine/gearbox/prop vibrates likes hell (like something is way way off balance) causing the whole car the vibrate. This can be cleared by dipping the
clutch, once this is done things resume to norm.
If the car is progressively accelerated to the same speed/rpm everything is fine with no vibration. If the engine is revved standing still, no
vibration anywhere.
I'm struggleing to pin point this as it only happens under hard conditions and shakes the whole car. Prop was balanced when made so unless
they've buggered things up that can be sort of discounted. Gearbox has just been reconditioned.
What I can't understand is that only occurs under hard accel/decel and can be cleared by briefly dipping the clutch.
Any suggestions very welcome.
Cheers
[Edited on 23/3/08 by darrens]
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Paul (Notts)
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| posted on 23/3/08 at 03:02 PM |
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Does it feel like its coming from the front or rear of the car.
Very long shot - but the rear driveshaft bolts on the whell cv joint sometimes clip the end of the upper wishbone when the rear end is compressed
down. I need to fit some stiffer sring on the rear to overcome this.
Look for a nice shiny gvrove on the underside of the upper rear wishbone .
Paul
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darrens
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| posted on 23/3/08 at 03:13 PM |
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quote:
Originally posted by Paul (Notts)
Does it feel like its coming from the front or rear of the car.
Very long shot - but the rear driveshaft bolts on the whell cv joint sometimes clip the end of the upper wishbone when the rear end is compressed
down. I need to fit some stiffer sring on the rear to overcome this.
Look for a nice shiny gvrove on the underside of the upper rear wishbone .
Paul
Paul,
Def not rear driveshaft, I had that problem when first built and rather than stiffen up or raise ride height I had the driveshafts and upper wishbones
modified slightly.
Once the vibration starts if you hold the rpm steady (but not accel or decel) the vibration continues, briefly dip the clutch and it disappears.
Am confused!
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TOO BADD
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| posted on 23/3/08 at 04:04 PM |
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Have you checked excessive play in the propshaft uj. Unloading and loading ?
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jollygreengiant
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| posted on 23/3/08 at 04:14 PM |
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Sound like you have answered the question your self, you just can't see it or you can't accept it OR you can't believe it.
It occurs if you sharp accellerate. -- it is obviously acceleration related.
It stays if you hold the revs until you dip the clutch. -- there is only a minimum number of items that would fit within these peramiters.
I think it is a problem with the clutch. Either with the plate or the cover. I think that you have some minor problem (at the moment) with the plate.
Shock or sudden acceleration is allowing or causing something to move out of ballance, (possibly a dust or oil or dirt build up) and while it has a
constant pressure applied it stays out of ballance. Dip the clutch and it is allowed to rotate/move back into ballance.
Does this make sense./ I hope this helps.
JGG
Enjoy.
quote:
Originally posted by darrens
quote:
Originally posted by Paul (Notts)
Does it feel like its coming from the front or rear of the car.
Very long shot - but the rear driveshaft bolts on the whell cv joint sometimes clip the end of the upper wishbone when the rear end is compressed
down. I need to fit some stiffer sring on the rear to overcome this.
Look for a nice shiny gvrove on the underside of the upper rear wishbone .
Paul
Paul,
Def not rear driveshaft, I had that problem when first built and rather than stiffen up or raise ride height I had the driveshafts and upper wishbones
modified slightly.
Once the vibration starts if you hold the rpm steady (but not accel or decel) the vibration continues, briefly dip the clutch and it disappears.
Am confused!
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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darrens
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| posted on 23/3/08 at 07:57 PM |
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quote:
Originally posted by jollygreengiant
Sound like you have answered the question your self, you just can't see it or you can't accept it OR you can't believe it.
It occurs if you sharp accellerate. -- it is obviously acceleration related.
It stays if you hold the revs until you dip the clutch. -- there is only a minimum number of items that would fit within these peramiters.
I think it is a problem with the clutch. Either with the plate or the cover. I think that you have some minor problem (at the moment) with the plate.
Shock or sudden acceleration is allowing or causing something to move out of ballance, (possibly a dust or oil or dirt build up) and while it has a
constant pressure applied it stays out of ballance. Dip the clutch and it is allowed to rotate/move back into ballance.
Does this make sense./ I hope this helps.
JGG
Enjoy.
quote:
Originally posted by darrens
quote:
Originally posted by Paul (Notts)
Does it feel like its coming from the front or rear of the car.
Very long shot - but the rear driveshaft bolts on the whell cv joint sometimes clip the end of the upper wishbone when the rear end is compressed
down. I need to fit some stiffer sring on the rear to overcome this.
Look for a nice shiny gvrove on the underside of the upper rear wishbone .
Paul
Paul,
Def not rear driveshaft, I had that problem when first built and rather than stiffen up or raise ride height I had the driveshafts and upper wishbones
modified slightly.
Once the vibration starts if you hold the rpm steady (but not accel or decel) the vibration continues, briefly dip the clutch and it disappears.
Am confused!
Makes perfect sense, and it is a good point, but how could a clutch/plate move. One half is bolted to the flywheel, which has locating pins on it (to
prevent misalignment) and the clutch plate fits over the gearbox spline.
On the other hand if under hard accel is it possible that the clutch plate isn't sitting flat, possibly caused by weak pressure plate.
Still head scratchin!!
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rusty nuts
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| posted on 23/3/08 at 08:12 PM |
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Doesn't sound like the prop but it might be worth checking that no balance weights have come off?
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omega 24 v6
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| posted on 23/3/08 at 08:29 PM |
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quote:
Makes perfect sense, and it is a good point, but how could a clutch/plate move. One half is bolted to the flywheel, which has locating pins on it (to
prevent misalignment) and the clutch plate fits over the gearbox spline.
BUT it could move IF the spigot bearing was not the correct internal dia to match the gearbox shaft OR if was not there at OR if it was fubared.
Also does the prop have a centre bearing (doubtful) but it could be weak or not up to the job and allowing the centre part of the prop to THROW itself
out (if you see what i mean.
Have to say though it certainly looks clutch orientated as I would have thought that as the revs/torque stabilised/reduced then it would wane away.
Dipping the clutch being the only way to cure it seems to point to where to look first.IMHO
If it looks wrong it probably is wrong.
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britishtrident
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| posted on 23/3/08 at 08:45 PM |
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Sound very much like a clutch problem --- three possible causes
(1) Spigot bush is missing after rebuild
(2) Springs on driven plate have broken
(3) Clutch diaphragm is loos or broken in cover plate.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Chippy
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| posted on 23/3/08 at 11:29 PM |
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Real PITA but I would bet that there is no spigot bush fitted, OR, its totaly nackered. Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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jollygreengiant
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| posted on 24/3/08 at 02:42 AM |
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It does not matter whether something is made by nature or mankind............ the fact that it was made means that it can fail. The where and when is
down to the part in question.........
Annon.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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richard thomas
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| posted on 24/3/08 at 01:04 PM |
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Engine mount close to failure? Disengaging the clutch will remove the rotational load on the block against the mounts...otherwise sounds like the
clutch - maybe springs on the way out, or the plate has become distorted?
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darrens
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| posted on 25/3/08 at 10:12 PM |
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quote:
Originally posted by Chippy
Real PITA but I would bet that there is no spigot bush fitted, OR, its totaly nackered. Ray
Feel a bit of a tart, but there ain't one fitted, can't believe I missed that. 
cheers for replies
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NeilP
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| posted on 25/3/08 at 11:14 PM |
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Darren,
Bloody obvious and sure you've done it but look carefully at the mainshaft spline and the front oil seal/bearing off your box as all that
wobblin' about can't be good - Jack up the rear wheels and turn the prop by hand using a gauge against the mainshaft to check for
bending.
The fact that it's not been happening long and that you've cleared it is hopefully going to mean that it's OK but worth checking
IMHO.
Cheers, Neil.
Edit: p.s. It's OK to feel a tart once in a while ... just don't tell the missus!
[Edited on 25/3/2008 by NeilP]
If you pay peanuts...
Mentale, yar? Yar, mentale!
Drive it like you stole it!
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Chippy
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| posted on 25/3/08 at 11:37 PM |
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quote:
Feel a bit of a tart, but there ain't one fitted, can't believe I missed that.
It's easy done mate, I bet that your engine was bolted to an auto box, and they don't have one fitted. Still hopefuly just put one in and
you will be fine, as long as the box hasn't been damaged. Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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darrens
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| posted on 26/3/08 at 08:04 AM |
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quote:
Originally posted by Chippy
quote:
Feel a bit of a tart, but there ain't one fitted, can't believe I missed that.
It's easy done mate, I bet that your engine was bolted to an auto box, and they don't have one fitted. Still hopefuly just put one in and
you will be fine, as long as the box hasn't been damaged. Cheers Ray
That makes me feel better, spun the prop to see if there was any movement in the shaft, all seems central so hopefully OK.
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