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  #1  
Old 13-09-2020, 09:58 PM
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137699 137699 is offline
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Default Drivetrain / diff clunk?

Done a search on this and can't find any posts with the same concern...

Often when I reverse I get a clunk from the rear - feels like it's in the area of the diff/propshaft. It doesn't happen as you select reverse, nor when you start to move, but when you ease of the throttle it happens then & feels like quite a shunt.

Doesn't do it every time but this seems to be a new sensation that's developed in the last few weeks. Diff clunks as the clutch is engaged seem to be a common "characteristic" but that's not what I'm getting.... just wondered if anyone had any thoughts?

As an aside, I also get an "ease-off" or "sudden throttle" knock sensation when travelling forward, e.g. being at 50mph in 5th - sudden let off of throttle a slight "knock" is detected - sudden floor of the accelerator and the same "knock" - almost as if something vibrating along the drive train line.

Not sure if this is connected? Thoughts anyone?
Just a little nervy about such issues give the boot floor problem, though mine has previously been strengthened....
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  #2  
Old 15-09-2020, 08:36 AM
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Guessing from the lack of response I have a unique issue here?
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  #3  
Old 15-09-2020, 08:55 AM
urquattrogus urquattrogus is offline
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Mine had a bit of a clunk/shunt although it was pretty much stopped when i removed the clutch delay valve which I felt made the clutch too slow/unresponsive when you change gear quickly.

Braided line with no CDV made quite a big difference.

I'm expecting the driveline to be further improved now I have replaced the guibo, centre bearing and the boot floor is re-inforced and has a new diff support ear, and Polybushes in the subframe to stop the subframe whipping about. Haven't got her back on the road yet though.



Other possible causes:

Worn Guibo/Donut
Incorrectly fitted Guibo/Donut
Worn Prop centre bearing.
Misaligned prop and or wear in the non greasable Universal Joint
Excess Backlash or play in the diff (unlikely unless abused)
Boot floor welds and or diff mount just starting to come away.

Guibo wise here is a useful video:

https://www.youtube.com/watch?v=Vw7Zbp1rfGI
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Old 15-09-2020, 12:04 PM
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The guibo was replaced a few months ago - also had the braided hose fitted.
The boot floor welds are my main concern - hopefully not that as it was all reinforced by a previous owner!
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  #5  
Old 15-09-2020, 12:27 PM
urquattrogus urquattrogus is offline
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Crossing my fingers for you, it's worth a look at the boot floor no doubt.

I had to look at mine very closely to spot the spot welds that were starting to fail.
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Old 15-09-2020, 01:26 PM
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I would say clunking just as you come off throttle/dip clutch and unload the driveline are common traits of the Z3 in general.
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Old 15-09-2020, 04:02 PM
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Defo, mines always done it. It can be disconcerting though...
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Old 15-09-2020, 08:08 PM
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Quote:
Originally Posted by c_w View Post
I would say clunking just as you come off throttle/dip clutch and unload the driveline are common traits of the Z3 in general.
I’d agree, mine has always done it, even when it was new to me at ~3.5 years old
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  #9  
Old 21-09-2020, 11:09 AM
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Mine does it, but its done 160k The garage said it was a bit of backlash in the gearbox.

It's fine once your rolling, but if you come on the throttle hard initially in any gear you feel the take-up.

All my diff bushes were fine and not holes in the floor etc
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