What is the awful noise?

[Cooper]

Hi Everyone,

I am going for the long-shot here, maybe someone knows the answer with to my question with the lousy explanation

When I accelerate REALLY [I mean peddle to the metal] hard with my 3.0 auto I often get this loud nasty sound coupled with some thumping type vibration. It reminds me of what it feels like when you run over a kangaroo or dog and you hear/feel it in the undercarriage. At first I thought it was the wheel loosing grip and vibrating the rear carrier or something. I suspect it is a very bad trans mount, note sure, nothing on youtube about this. Note:

I don't seem to loose power or thrust.
Not an engine noise, seems to be left side passenger area but who knows.
Sometimes it is for a fraction of a second, sometimes almost 1 second
I think it is when i change from 1st to 2nd but not sure.
No issues when going fast, light to moderate acceleration, even spirited acceleration.
Idles and rides perfectly except for this.

I think if it was the dif it would just shred out and miss then destroy itself. So unlikely???
Auto box? Seems really strong but could this be the issue? No other noises or slipping etc I can sense.
Shocks were inspected and seem good, and sound is low, not high up where the rear shocks mount [i think]

any idea folks?

I need to get this resolved so I don't embarrass myself when a ricer challenges me and I thrash him in a hail of dust and noise.

Cheers, Graeme

 

[t-tony]

Have you checked prop. shaft joints ?

Tony.

 

[Cooper]

Have you checked prop. shaft joints ? Tony.

From memory the U joint was replaced, I will have to hoist her and get it checked, thanks for the idea.

 

[raymond]

Diff mounting failure is possibe although usually seen on the M cars
http://forums.pelicanparts.com/bmw-z3-z4-forum/109101-z3-differential-mount-broken-loose.html

 

[littlefeller]

hopefully its something simple like for instance the weights that are in the rear bumper, or rather behind it, these are rubber mounted and can fail. some people have spent an absolute age trying to find a thumping noise cause only to find these are the culprit.

 

[gookah]

check boot floor spot welds

 

[Ianmc]

Is your dog safe?

 

[Cooper]

Not my dog, but the outcome was not good, nor for the rabbits, or the possum.

 

[Ianmc]

We had possums in the garden when we lived in NSW, a bit dopy. Didn't realise they got to Taz.

 

[Cooper]

We had possums in the garden when we lived in NSW, a bit dopy. Didn't realise they got to Taz.

Come and get as many as you like

 

[Cooper]

He everyone, I have been following up on a few leads given here and on one youtube vid there was complete failure of the boot rivets and dif carrier. I mean a complete separation which I don't have in this car. This resulted in a 'squeak squeak' when he rocked it back and forth followed by the statement if you here this then you are already late for the party. Anyway, when I get out of the car I sometimes here that squeak, but I also heard that in my 2.2i. Anyone else ever hear a squeak when they get out [from the suspension]. ???

 

[Ianmc]

No!

 

[littlefeller]

yep, mine squeeks, mine is the rear suspension.

 

[gookah]

squeak can be handbrake sometimes

 

[oldcarman]

Likely just the rear suspension squeaking as the drivers side lifts as you exit!! JIM

 

[Cooper]

Thanks guys. It is the handbrake, thankfully. On a brighter note the car does not make any sounds when going over precarious speed bumps even when going over them on an angle. I now suspect it is one of the drive train joints as suggested above or a mount. Next step is YouTube training on how to test then up on stands she goes.

 

[t-tony]

Thanks guys. It is the handbrake, thankfully. On a brighter note the car does not make any sounds when going over precarious speed bumps even when going over them on an angle. I now suspect it is one of the drive train joints as suggested above or a mount. Next step is YouTube training on how to test then up on stands she goes.

If you put a trolley jack under the diff and raise the car you should be able to see if the diff bush is moving excessively.

Tony.

 

[NZ00Z3]

Hi

For the Z3, Suggest you check out the following:
- Center drive shaft bearing.

- Flexi-drive, that round rubber item between the drive shaft and transmission

- Rear sub-frame bushings. With the 3.0L you have lots of torque and HP. When you peddle to the metal, its the left side of the sub-frame that wants to lift. If you have the original rubber bushings, they may be soft and you are bouncing them on the end stops. Remember its the left side of the boot/cross member that fails on the manual MZ3's. If you look at the spec's you'll see that your 3.0L is only just a couple of hp and Nm short of the USA S52 powered MZ3's (common boot weld failure cars), so your car has sufficient power to break the boot welds if you abuse it. Suggest that you consider fitting some poly rear sub-frame bushings as preventative maintenance. Leave the diff bushing as OEM rubber.

I've also have a few (thousand) Ozzy possums around here you can have back. They just eat too many trees.

Regards

Muzz

 

[lightning]

Did you make sure the dampers/shocks are OK?
If one has failed you might get wheel tramp on full power acceleration.
l had this on my Porsche 928 which was an auto, and it turned out that the O/S rear shock was not working.
Although on the Z3 3.0 the traction control should kick in if this happens.

 

[Cooper]

Good news people

I got the local mechanic to hoist and inspect, he also let me tinker around. It is all clean and tidy and tight under there. The only thing that is suspect is the center shaft carrier bearing rubber so the tail shaft sags a bit. Once full power is applied and it changes from 1st to 2nd gear the small amount of movement causes the very brief vibration. It will be fixed for a total of AUD$182 on the 12th. For that price I will get him to do it as the exhaust has to be dropped and the shaft removed. Will only take him about 1.5 hours and I get to help!

Thanks for the support everyone.