Ive been bangin this drum for weeks now, and im still im no closer to resolving this horrible noise that happens when i come of the power from
anything above 50/60mph, despite being £175 worse after an advised diff rebuild, and having given one of the tunnel uprights a shave as i thought the
prop was too close and could be vibrating against it.
Link to Video of the Noise
Scroll down to the large video at the bottom of the page.
Ther is definately nothing touching the prop, so it must be something resonating up the prop.
Today i decided to remove the prop and investigate further, and now ive discovered a design floor in my BEC chassis. I cant get the prop out i one
piece without removing the engine, as ive left the lower rail in the tunnel at the very end of the foorwells. In the Locost book it shows it removed,
but in my wisdom i thought id leave it for extra strength. Its the one that joins the 2 footwells together.
Does anyone have any thought s on how vital this small bit of tube is?
Does anyone know know what the effect of a knackered output shaft bearing would be on a Yamaha R1 engine.
Im right up against it now, to the point where i could sell the f....ing thing and buy a production sportscar, a cheap one at that, but seriously,
this is driving me mad, i just cant find the source of the noise.
Please help.
Chris
[Edited on 20/5/08 by ChrisS]
Has the prop been balanced?
It might be this if it is only occurring at certain speeds.
The prop is a standard rear section from a Sierra, with an MK front section, MK supplied the whole thing.
So really the answer is i dont know if they balance them, although i have just noticed the rear balance weight appears to be 3/4 missing. Well its
only 3/4 the size of the front one, and is spot welded on, looks like manufacturer original, although that doesnt really tell much i guess.
Sounds like there might be something inside? Does it rattle when u take it off?
Have it balanced and see what happens? If its not quite true it will make alsorts of strange things happen.
Check our engine mounts& bell housing, Sounds like movement on the prop causing it to rub of skif on the frame .
or COuld it be the blanking plate between the engine and gear box catching the back of the flywheel
Certainly sound like thin metal vibrating or skiffing rather than a large mass (propshaft) being thown about.
I had problems with out of balance prop and it burst the lug off of the engine block on the drivers side and cracked the bell housing also damaged the
engine mounts due to the fatigue. Mine sounded more like a deep knock.
[Edited on 7/505/08 by mad4x4]
have you checked for touching on the center bearing?sounds like the prop is moving backwards and forwards and the crap guard is rubbing on said center
bearing
Yikes!
Nasty, but as said does not sound like terminal gearbox, prop or diff failure.
Much more like something catching, though I would expect you to be able to see some rub marks somewhere if that was the case?
quote:
Originally posted by ChrisS
The prop is a standard rear section from a Sierra, with an MK front section, MK supplied the whole thing.
So really the answer is i dont know if they balance them, although i have just noticed the rear balance weight appears to be 3/4 missing. Well its only 3/4 the size of the front one, and is spot welded on, looks like manufacturer original, although that doesnt really tell much i guess.
Could be the big nut that holds the prop adapter to engine is loose or bolt in prop by centremount that holds the two peices of prop together
[Edited on 7/5/08 by CRAIGR]
I thought it could be the prop adapter nut, and its not, checked today and its tight.
I thought it could be the prop centre bearing bolt, but that also seems to be tight.
Dipping the clutch seems to make a small amount of difference to the noise, but it doesnt silence it.
i did pop the clutch plate/cover recently by accident and had to take the cover off and put it back, is there anything i could have put back wrong? I
thought it looked straight forward.
This is driving me metal, if i had matches, id toast the f..ker
If the noise appeared after clutch checked id go back to clutch and recheck all that again.
From the noise i heard sounds tinny, like heatshield vibrating.
When i was a technician, i could build revs up and make a exhaust resonate on a ramp and hold the noise until someone bent a heatshield out of the
way.
I dont think its prop or transmission noise.
From what I can hear, when under load and being operated in normal mode.... it doesn't sound at all bad. In fact, doesn't sound that bad
throughout. Gotta be something vibrating.
I consume Westfield gearboxes at a frightening rate, even when 'fresh' they vibrate, whine and generally try to out drown the noise from the
vibrating alloy panels (floor pan etc.). When the flanges wear on the splines, the bearings start breaking up, or the thing just randomly loses all
it's oil down the tunnel - the noise and vibes are just unbelievable.
Full throttle is the only way to get rid of most clunkage and whineage...
Yeh it's a bec isn't it? They all sound like that. Put a crossflow in it and all will be well.
Just a thought.
I know you've said the adaptor nut is tight, but are you sure the adaptor is tightening up fully, some need spacers behing them so they do?
Was gonna add - can the flange adaptor slide backwards and forwards slightly on the gearbox output spline, even though the nut is tight?
That's what happened to mine and I thought it was a prop/diff problem.
Pat...
Just seen the vid - is that the prop wobbling around?
If so - that's not good.
You have got a centre bearing haven't you?
Pat...
Trouble is the noise was there from the start, the very day i drove to SVA, and the clutch popped in before that day., so i couldnt say if the clutch
has anything to do with it. It seems to work fine so i dont think its this?
The sprocket adapter is most definatlety tight, i cant lever it at all.
This all seems to point to the prop, maybe the centre bearing. Im gonna check it out as soon as i can get the prop out from the tunnel. (Thats another
issue.)
Any thoughts on my mention of the output shaft bearing on the bike engine being knackered? I dont know what effect this would have.
quote:
Originally posted by Avoneer
Just seen the vid - is that the prop wobbling around?
If so - that's not good.
You have got a centre bearing haven't you
Pat...
It's hard to tell but it looks as if the prop shaft is weaving about all over the place. If so, irrespective of the noise, I should fix it, for
the sake of your legs.
Why not do another video with the camera fixed looking at the propshaft. It's very hard to see what's going on with the camera waving
about.
Edit
Oh sorry - the Large video
I was looking at the thumbnail which seems to show the centre weaving.
Ditto as above but focus on the centre.
[Edited on 8/5/08 by Macbeast]
quote:
Originally posted by Macbeast
It's hard to tell but it looks as if the prop shaft is weaving about all over the place. If so, irrespective of the noise, I should fix it, for the sake of your legs.
Why not do another video with the camera fixed looking at the propshaft. It's very hard to see what's going on with the camera waving about.
Edit
Oh sorry - the Large video
I was looking at the thumbnail which seems to show the centre weaving.
Ditto as above but focus on the centre.
[Edited on 8/5/08 by Macbeast]
Ah - watched the right vid now.
Very strange, but does definately sound like a thin piece of metal vibrating and nothing to do with the prop.
Pat...
mine sounds quite noisey like yours with some knocking going on when i come of throttle doing that sort of speed 30 - 50mph mine was supplied by m.k
maybe i should be taking mine of and taking it to get balanced as well .
i could not see anything wrong with it no play ect either .
Turns out that this was all due to 2 knackered UJ's on the rear section of the prop, and the fact that the entire prop including the
"new" front section was completely unbalanced
I find it hard to believe that you can buy a prop from a reputable company and have such problems with it, believing that what youve been supplied
surely couldnt be the problem.
Anyway at least the car is now driving as it should be.
Thanks for everyones help, especialy those who suggested a prop balance.
Chris
Chris, thanks for the update.
Too often problem threads are just left hanging and we never know what the outcome is. Glad you're sorted 
yep, glad to hear its sorted, and use your experience to guide your future purchases!!
If its cheap, its probably crap!