Strange noise in the rear

jp928 · Postby **jp928** » Sat Apr 21, 2018 2:58 pm

92 NA6, 185k kms. Been with us since 2004. Over the last year or so its developed a noise in the rear under braking. Suspected brakes, replaced front rotors, all pads. Seemed to go away, but has returned. Happens at low speed - moving back and forth in the driveway, mechanical sounding grunch. The wheel bearings, hubs, shocks etc all seem secure. Driver seat is rigid. Happens with both softtop and hardtop fitted, although the topside roll bar has been ribbing on the hardtop quite a bit. Cannot see anything underneath moving....except one thing. There are witness marks of something rubbing on the ARB near the bushes, as though its touching the subframe somehow. Clearance is probably < 2mm. I have put some whiteout on the rub marks on the bar and will check next week for signs of contact.
Anybody seen anything like this please, and did you find the culprit?
thanks
jp

bruce · Postby **bruce** » Sat Apr 21, 2018 3:05 pm

Empty out your boot and car.
Could be the diff.

RS2000 · Postby **RS2000** » Sat Apr 21, 2018 3:42 pm

jp928 wrote: Happens at low speed - moving back and forth in the driveway, mechanical sounding grunch. The wheel bearings, hubs, shocks etc all seem secure.

My guess is a rear wheel bearing.
I had the same thing with my NB8A track car when I bought it. There was no movement in the hubs, but one side was slightly noisier than the other when rotating back & forward by hand, & it proved to be the culprit.

93_Clubman · Postby **93_Clubman** » Sun Apr 22, 2018 1:03 pm

Are we talking a particular side? Re the noise as opposed to the marks, might be worth keeping in mind that the rear pside (on RHD) caliper can drag due to internal corrosion associated with the handbrake mechanism in the caliper.

manga_blue · Postby **manga_blue** » Sun Apr 22, 2018 3:43 pm

Could easily be a wheel bearing. The first sign is that it makes more noise when you corner in one direction. e.g turn right and a bad left side bearing will make more noise, turn left and a right bearing does it. After that it's almost impossible sometimes to pick front from back. I had a blown left front bearing that convinced the the diff was dying - all the noise was transmitting through the body to the boot floor. Once you have narrowed it down to one side then jack up each wheel, take the wheel off and pry the brake pads away from the disk far enough that they don't rub. You should be able to feel a little roughness when you turn the wheel by hand.