Knocking on acceleration and deceleration

[Dino D]

No i brought this one.
View attachment 24211
It lists for the z3 chassis Same manufacturer but different fitment bolt on rather than push in

I bought this one and it good- wide enough to just meet the slightly wonk clutch pedal (pedal bushings are likely worn so will eventually need doing).
Only thing I've noticed is that it doesn't screw in very far on my car, maybe 2-3 turns only. That's ok as it just right for my clutch action but if I need the bite point a bit lower later on then I'll have to look at why I can't screw it in further.

 

[Dino D]

Back to the original topic of the clunk.
At 120k miles I'd check the diff mount bush that's worn. Mine was practically falling out at 110k miles.
I have a new bush in there but there is a characteristic mechanical feel/sound to the driveline that can be heard when the hood us up and at low speed. It's not loud though, a passenger would really notice but I do as I look out for it. It was also there on my low mileage e46 330i (but much more suppressed in a car that big and refined relative the the Z3).
Before the bush was replaced on the Z3 it was very audible, actually sounded like a rattle which threw me off.

The Guibo (proshaft donut) is also an item to check.

Not sure how you check these though.

 

[PeteZ3]

Back to the original topic of the clunk.
At 120k miles I'd check the diff mount bush that's worn. Mine was practically falling out at 110k miles.
I have a new bush in there but there is a characteristic mechanical feel/sound to the driveline that can be heard when the hood us up and at low speed. It's not loud though, a passenger would really notice but I do as I look out for it. It was also there on my low mileage e46 330i (but much more suppressed in a car that big and refined relative the the Z3).
Before the bush was replaced on the Z3 it was very audible, actually sounded like a rattle which threw me off.

The Guibo (proshaft donut) is also an item to check.

Not sure how you check these though.

thanks for the info, ill look into both!

 

[t-tony]

Back to the original topic of the clunk.
At 120k miles I'd check the diff mount bush that's worn. Mine was practically falling out at 110k miles.
I have a new bush in there but there is a characteristic mechanical feel/sound to the driveline that can be heard when the hood us up and at low speed. It's not loud though, a passenger would really notice but I do as I look out for it. It was also there on my low mileage e46 330i (but much more suppressed in a car that big and refined relative the the Z3).
Before the bush was replaced on the Z3 it was very audible, actually sounded like a rattle which threw me off.

The Guibo (proshaft donut) is also an item to check.

Not sure how you check these though.

When the guibo is at the end of its life it will start to crack and even become unbonded. It will be fairly obvious too.

Tony.

 

[zedonist]

It sounds like DMF and clutch bearing noise to me, if left the DMF can explode or the bearing can wear the lay shaft in the gear box, theses cars should not knock or rattle, so it needs to be diagnosed correctly and treated before it is an expensive failure.

 

[t-tony]

It sounds like DMF and clutch bearing noise to me, if left the DMF can explode or the bearing can wear the lay shaft in the gear box, theses cars should not knock or rattle, so it needs to be diagnosed correctly and treated before it is an expensive failure.

Certainly not impossible but in my experience unlikely. When a DMF fails you will invariably get some vibration through the transmission as the seperate parts of the flywheel work out of sync with each other. Sometimes the seperate parts move to their furthest point out of position and stitch there, which again throws it out of balance and causes vibration. A problem highlighted just this afternoon on my daughters Insignia. I've never heard a single clunk or knock from a dual mass up to now, and I've heard a lot!

Tony.

 

[zedonist]

I had to have a new gear box on my T5 due to a knackered DMF and bearing Tony, I was told that I was lucky ad normally they just let go and punch a hole in the casing, so on mine, they refurbed the lay shaft. Quite a number on the forum have been unlucky, and needed a new case as well, which is not cheap, in all instances the DMF and bearing knocked and rattled and people ignored it.

It may not be the case on this Z3, but it should not nock and rattle and should get diagnosed early...

 

[t-tony]

Agreed if there's something happening which shouldn't it's much better to get it diagnosed properly Rich. The VW gearbox isn't one of the strongest out there and don't take much abuse so again best caught early.
A vibration is always the first indication that all is not well, as in the Insignia. Guess that'll be a job for Dad then!

Tony.

 

[Antm72]

In my case the knock is definatly drive shaft related as you can feel it and recreate it in the drive shaft the guibo is good it is just take up of slack in a drive train the car drives flawless no vibration no noise from the box or the from the bearings.
Its not something i say should be there but it gets no worse and with out a complete drive train rebuild its unlikely to fix.
The diff and rear end drive is good if i grab the prop its in that so i suspect spline wear as no other symtom at all.

 

[Grumps]

My 2.8 has a knock when cold. Does it everytime I pull off the drive from cold. I'm not as mechanically minded as @t-tony and @Antm72 but I'd say it definitely comes from the diff area rather than it being gearbox/clutch related. It only does it a few times and once warmed up it never does it. I've had the car for 3 years and it's never got any worse so I'm not concerned. If it does however start to deteriorate I shall certainly get it checked. It does seem an extremely popular issue with the 2.8, I've read it several times on here and on the dark side but i've never heard of a total failure due to it. Maybe it's just one of those things.

 

[5harp3y]

It's slack in the drivetrain, mines on 70k and does it

Mostly when cold but noticeable when warm.

I suspect that engine, gearbox and diff mounts are all past their best leading to more of a noise.

Guibo cab add to the noise too

I certainly wouldn't worry about your dmf exploding!!

 

[PeteZ3]

Thanks for all the help, I'll look into all of these this weekend, I'm thinking I may have to take it to a garage to get checked out.... This is perhaps going slightly beyond my knowlage and skill set. I just want to get it diagnosed correctly before I go buying parts and wasting money. I don't even know what a DMF is??? Lol

 

[oldcarman]

Dual Mass Flywheel!! @PeteZ3 ! JIM

 

[zedonist]

If something is knocking or rattling then it is either loose, worn or broken. On this basis it needs to be tightened, fixed or replaced. Experience tells me that ignoring it, the problem gets worse and more expensive...

 

[Antm72]

The clutch stop arrived at the weekend and had time today to get it fitted.
It makes a real difference to the way the car feels to drive makes the gear change feel very precise a great mod and cheap as chips !!!

 

[PeteZ3]

nice one! ill get one next month, im literally skint after december.... every time!! haha.... im curretly working on the zed actually, ive just had two new front tyres so ive decided to have a look under the track rod boot... well its got a bit of oil in it from the stearing rack power steering fluid is leaking in, so ive drained it out, cleaned it all up and will see how bad the leak is. ive filled the power steeing up, which was nearly full anyway, so im not too worried.


CLUNK QUESTION
with regards too the clunk, its stayed the same and ive not had the chance to do any exploring with regards to the DMF or the doughnut.... ive had a go at turning the drive shaft, and i can turn it back and forth (clockwise and anticlockwise) quite easily using just my hand... anybody know if this s normal?!? when I do so I can hear the same clunk I hear when im driving it. maybe this sheds some light on the problem a little bit?

input on that from anybody would be great,

Pete

 

[zedonist]

Sounds like backlash in the diff, try a mechanics stethoscope to be sure, sounds like you have narrowed it down. you need some back lash in the diff as when it heats up it does not seize,

 

[Bozzy]

The clutch stop arrived at the weekend and had time today to get it fitted.
It makes a real difference to the way the car feels to drive makes the gear change feel very precise a great mod and cheap as chips !!!

I've just ordered one Ant,hope it works as well on mine


Steve

 

[PeteZ3]

right, ive just installed a new diff mount baring. but i am totally stumed as to what oil to put in my diff!!!! any help please, ive been to my local BMW dealer and that department was closed temporarily so no one could help me! so input here would be greatly appriciated! thank you to ev eryone that has helped me so far! my zed loves you for it! haha

 

[BMBabe]

@GazHyde @Lee @t-tony