Clunk from the back end

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Chris
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Clunk from the back end

Post by Chris »

A few miles from home the other week, doing 30 and started hearing a quiet clunk from the back end.

As we slowed and pulled over it got louder and was coincident with the driveshaft or wheel rotation (still on RGBs - post 63 setup)

Nothing obviously amiss so we set off home again and from a start the clunk is really quite loud, getting quieter at speed I suppose because of the inertial torque being high from a standing start.

Up on stands now, wheels off, nothing external appears loose, and running the drivetrain at low speed produces no clunk at all, but of course there is no road resistance.

So where next - any ideas from the floor as what it could be?
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Re: Clunk from the back end

Post by vwJim »

Start with the easy stuff, check the handbrake I operation / remove the drums / inspect the mechanism / hub splines etc.

Support the driveshafts at running height / level, drain the reduction boxes / check the oil for debris / replace with new
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Chris
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Re: Clunk from the back end

Post by Chris »

Thanks Jim, will investigate, just seemed quite a big noise to be brakes but you never know.

Just read a thread on the Samba about worn fulcrum plates causing a definite clunk...
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Re: Clunk from the back end

Post by philsparks »

Hi Chris

You are describing exactly what I had. And it was the fulcrum plates.

Regards Phil

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Re: Clunk from the back end

Post by Chris »

Thanks Phil. Haven't investigated yet but was that a trans-out job?
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Re: Clunk from the back end

Post by richandsue »

Are the spring plate bolts all tight.

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Re: Clunk from the back end

Post by Chris »

Yes; all obvious bolts checked.

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Re: Clunk from the back end

Post by BJ1 »

Chris wrote:
Tue Sep 17, 2019 8:28 pm
Thanks Phil. Haven't investigated yet but was that a trans-out job?
It is I'm afraid - pull the motor then the trans. Takes a full day with help from one other.
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Re: Clunk from the back end

Post by Chris »

As usual, took me ages to get going, but I took the gearbox out and fulcrum plates etc looked absolutely fine. The locating bolts into the solid front mount were loose though, not sure if associated movement could have caused a noise though.

Jim - would it be worth fitting one of the early mount polyeurethane adapters you have? Gearbox is AH code. The old housing has been cut - this won't effect the fit will it?
IMG_20200406_174246.jpg
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Re: Clunk from the back end

Post by richandsue »

i don't like the sound of those urethane gearbox mounts. heard so many stories that they are too hard and give a lot of engine/road noise through the chassis. never tried them but would love to hear if anybody can confirm this.

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Re: Clunk from the back end

Post by vwJim »

richandsue wrote:
Thu Apr 09, 2020 4:11 pm
i don't like the sound of those urethane gearbox mounts. heard so many stories that they are too hard and give a lot of engine/road noise through the chassis. never tried them but would love to hear if anybody can confirm this.
Late bus urethane mounts are rubbish. Never fit them.

But the lollipop mounts, even though they're urethane, transmit FAR less noise than a solid mount.
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Re: Clunk from the back end

Post by vwJim »

Chris wrote:
Thu Apr 09, 2020 1:00 pm
As usual, took me ages to get going, but I took the gearbox out and fulcrum plates etc looked absolutely fine. The locating bolts into the solid front mount were loose though, not sure if associated movement could have caused a noise though.

Jim - would it be worth fitting one of the early mount polyeurethane adapters you have? Gearbox is AH code. The old housing has been cut - this won't effect the fit will it?

IMG_20200406_174246.jpg

Chris,

If the bolts were loose and there was enough slop in the holes then that can cause a knock as it moves or allows the linkage to knock etc. But not speed related rotational knock.

Bad news though is there's nothing really left of your early mounting. Someone really hacked that out good and proper!

What I'd do is,

1. Re-mount the gearbox on the solid mount
2. Install a mid-mount
3. Remove the gearbox to allow you to cut off all that previous mount arrangement so you have less noise without the solid mount there.
4. Reinstall gearbox and engine etc.

Then drive it. IMHO a mid mount will be enough, but if you want to go to town on it,

3.1 Re-mount gearbox again, this time on the mid mount, and position a late split front mount on the nosecone / tack weld an adapter bracket in plate
3.2 Remove the gearbox, weld the new adapter in place fully
3.3 Finally mount the gearbox on the new front late bus mount & mid mount
4. Engine etc

I've an early bus here that runs a welded in adapter mount structure to use a late rubber mount with a mid mount.
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Re: Clunk from the back end

Post by dg »

Had the same clunk noise some years ago, my issue was due to reduction box bearings failing.

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