Knock noise when I reverse and then brake

[Nic_s]

When I reverse and then brake, like when you do in a parking lot, there is a knock noise coming from the back. It sounds like it's coming from the left rear wheel, but I can't be sure.

I think it's getting loader as well. Was wondering if anyone else have ever had such an issue and how would I fix it?

Thanks

 

[plonkster]

small stone between brake mechanism and backing plate. Don a dust mask, and get in there with some compressed air.

Or (like on mine) the brake shoes for the handbrake is acting up in some manner. Mine makes an annoying mosquito like whine above 40km/h. My mechanic could not get it to shut up, its been like that for the last 10k km and I'm ignoring it

 

[Rapido WP]

3 Weeks ago I had exactly the same noise when reversing & braking on my E46 330i, and AA replaced the rear shocks and mountings, PLUS they replaced the diff.
I now still dont know for sure if the knock came from the worn shock mountings or the diff. What must be related to the diff problem is that the month before the new diff was put in, they replaced the right side- shaft, which had been making a loud ticking noise, not unlike a shot CV joint. Hopefully its your shock or mounting on the one side.

 

[BimmerMan]

When I reverse and then brake, like when you do in a parking lot, there is a knock noise coming from the back. It sounds like it's coming from the left rear wheel, but I can't be sure.

I think it's getting loader as well. Was wondering if anyone else have ever had such an issue and how would I fix it?

Thanks

My E30 does this aswell. I thought it was either the handbrake shoes, diff mounts or the gearbox mounts. Never got around to troubleshooting it though...

 

[Jandre]

When I reverse and then brake, like when you do in a parking lot, there is a knock noise coming from the back. It sounds like it's coming from the left rear wheel, but I can't be sure.

I think it's getting loader as well. Was wondering if anyone else have ever had such an issue and how would I fix it?

Thanks

My E30 does this aswell. I thought it was either the handbrake shoes, diff mounts or the gearbox mounts. Never got around to troubleshooting it though...

I was also heading in that direction. Sticky handbrake.

 

[Nic_s]

3 Weeks ago I had exactly the same noise when reversing & braking on my E46 330i, and AA replaced the rear shocks and mountings, PLUS they replaced the diff.
I now still dont know for sure if the knock came from the worn shock mountings or the diff. What must be related to the diff problem is that the month before the new diff was put in, they replaced the right side- shaft, which had been making a loud ticking noise, not unlike a shot CV joint. Hopefully its your shock or mounting on the one side.

I thought about shock mountings, but shouldn't be making knocking noises as I drive over bumps as well?

EDIT: I've got drum brakes at the back. I had new brake shoes put in last year. I don't really understand how it can be the diff mount. The doesn't move and should be affected by braking forces... should it?

 

[BimmerMan]

3 Weeks ago I had exactly the same noise when reversing & braking on my E46 330i, and AA replaced the rear shocks and mountings, PLUS they replaced the diff.
I now still dont know for sure if the knock came from the worn shock mountings or the diff. What must be related to the diff problem is that the month before the new diff was put in, they replaced the right side- shaft, which had been making a loud ticking noise, not unlike a shot CV joint. Hopefully its your shock or mounting on the one side.

I thought about shock mountings, but shouldn't be making knocking noises as I drive over bumps as well?

EDIT: I've got drum brakes at the back. I had new brake shoes put in last year. I don't really understand how it can be the diff mount. The doesn't move and should be affected by braking forces... should it?

Its the transfer of weight on different parts of the car that will cause the knock if its something to do with diff or gearbox mounts. Maybe try reversing up to a bit higher speed in an open parking lot and then hitting the brakes. See if you can hear the knocking any clearer the faster you go? When you brake in Reverse, the weight is being thrown onto the rear of the car instead of the front as with everyday, normal braking.

Could be talking rubbish, but that is what I would be looking at.

 

[Nic_s]

3 Weeks ago I had exactly the same noise when reversing & braking on my E46 330i, and AA replaced the rear shocks and mountings, PLUS they replaced the diff.
I now still dont know for sure if the knock came from the worn shock mountings or the diff. What must be related to the diff problem is that the month before the new diff was put in, they replaced the right side- shaft, which had been making a loud ticking noise, not unlike a shot CV joint. Hopefully its your shock or mounting on the one side.

I thought about shock mountings, but shouldn't be making knocking noises as I drive over bumps as well?

EDIT: I've got drum brakes at the back. I had new brake shoes put in last year. I don't really understand how it can be the diff mount. The doesn't move and should be affected by braking forces... should it?

Its the transfer of weight on different parts of the car that will cause the knock if its something to do with diff or gearbox mounts. Maybe try reversing up to a bit higher speed in an open parking lot and then hitting the brakes. See if you can hear the knocking any clearer the faster you go? When you brake in Reverse, the weight is being thrown onto the rear of the car instead of the front as with everyday, normal braking.

Could be talking rubbish, but that is what I would be looking at.

It does seem to be loader when I reverse faster or brake harder. Thing is, the wheels are connected to the hubs, the hubs are connected to the trailing arms, the trailing arms are connected to the rear sub frame, and the rear sub frame is connected to the chassis. The only connection between the diff and the wheels as far as I can see are the side shafts. So if you brake or accelerate the forces of that is transfered through the trailing arms to the Sub frame to the chassis. This is my understanding though... :mmm:

I'll crawl under the car again, in some older clothes this time, and then pull at some bits to see if something might not be loose. :thumbsup: