General What is this noise

[El cargador]

Hi All. My car has suddenly developed a knocking noise from the rear end. It sounds like a tapping on the bodywork.it only happens on deceleration and is constant with the car speed. Push in the clutch and it's still there. Pull the handbrake whilst it's moving and it goes away. I've jacked up both wheels and tried spinning them and no noise. I can't tell if it's coming from one side or the other.any ideas please.

 

[El cargador]

Update.... Just been out with a mate to let him hear it and it's stopped doing it (isn't that always the way).

 

[Peter Pick-Up]

It's like going to the dentist...

 

[El cargador]

Strange ..just been out on my own and it's back

 

[turbo500]

Could it be 'weight' dependent? So under light load it's knocking or touching something? Maybe something suspension related is loose? Or maybe some debris is stuck somewhere (jammed around the brakes or axles)?

 

[El cargador]

I've looked underneath nothing there or loose that i can see. And nothing looking as it's rubbing, It must be weight related as it did'nt do it with a passenger , it is quite noticeable

 

[giardini]

Hi El Cargador, just an idea, as you say "It happens only on deceleration":

Could it be that when the torque reaction tilts the engine, something then contacts and knocks on the bodywork ?
I've had this happen with my Giardiniera, it was the exhaust touching the rear crossmember...

 

[1500500]

I had the same noise. not enough grease on splines on the driveshaft or the spines are worn

Have you replaced them.

Having the extra person in the car probably levels out the angle of the driveshaft meaning it’s less likely to be noisy

Cheers



Geoff

 

[El cargador]

I am thinking it maybe the rubber joints on the axle because
A. I didn't replace them (or the wheel bearings when I restored it)
B. When I pull away ,just as the clutch comes to take full weight of car, it lunges forward just slightly.
Someone suggested the wheel geometry which I had set in a tyre shop about 3 weeks ago(the noise appeared only 3 days ago though)
I know 1 of the rear seals is leaking grease at the back of the stub axle.

 

[El cargador]

Hi El Cargador, just an idea, as you say "It happens only on deceleration":

Could it be that when the torque reaction tilts the engine, something then contacts and knocks on the bodywork ?
I've had this happen with my Giardiniera, it was the exhaust touching the rear crossmember...

Hi Giardini I thought it maybe the bottom of the fan casing touching the bottom tinwork as it had before but I jammed a rag in there but it was still happening. I may order an uprated spring just in case

 

[El cargador]

Another thing i was thinking is , as i was underneath the rear yesterday ( I seem to spend a lot of time there lately) I noticed the bottom bolt of the shock absorber,although the nut was tight the rubber donuts were moveable . Could be this?

 

[El cargador]

Hi El Cargador, just an idea, as you say "It happens only on deceleration":

Could it be that when the torque reaction tilts the engine, something then contacts and knocks on the bodywork ?
I've had this happen with my Giardiniera, it was the exhaust touching the rear crossmember...

Hi giardini. It seems the noise only appears after the car has been driven for a while. Yesterday I pulled into the ind. Est. Whilst the car was rolling slowly I turned of the engine and it was still there. If I push it ( engine off) I can't hear anything, so it must be bearings / hub or axle/gearbox??

 

[giardini]

Another thing i was thinking is , as i was underneath the rear yesterday ( I seem to spend a lot of time there lately) I noticed the bottom bolt of the shock absorber,although the nut was tight the rubber donuts were moveable . Could be this?

The doughnuts are on the unthreaded part of the rod and should be firmly pinched, if the nut is tight and you can spin them easily, then the rubber has hardened or perished and should be replaced. (Kits from Ricambi)
It doesn't explain the rhythmic knocking you describe, though.
The noise ceasing when you apply the hanbrake seems to point to the hub bearings.
This is where you wish you had a trained monkey you could strap underneath the car to point to the culprit !

 

[El cargador]

The doughnuts are on the unthreaded part of the rod and should be firmly pinched, if the nut is tight and you can spin them easily, then the rubber has hardened or perished and should be replaced. (Kits from Ricambi)
It doesn't explain the rhythmic knocking you describe, though.
The noise ceasing when you apply the hanbrake seems to point to the hub bearings.
This is where you wish you had a trained monkey you could strap underneath the car to point to the culprit !

Giardini. All rubber on the car is new

 

[Franko500]

My new shock absorbers had a similar issue on the rear. I kept hearing a knocking noise when going over any bumps. The rubbers were loose. I ended up cutting 1mm off the length of the tube spacer. This allowed the rubbers to be squeezed tight and the knocking stopped. If the noise stops when you have a passenger, then you could always drive around with a bag of sand in the passenger side.

 

[giardini]

Giardini. All rubber on the car is new

El Cargador. Then the bushes should be very tight.

 

[giardini]

My new shock absorbers had a similar issue on the rear. I kept hearing a knocking noise when going over any bumps. The rubbers were loose. I ended up cutting 1mm off the length of the tube spacer. This allowed the rubbers to be squeezed tight and the knocking stopped. If the noise stops when you have a passenger, then you could always drive around with a bag of sand in the passenger side.

Oh, Sean !!! The sand bag is a terrible fix !!! Replacement bushes kits are dirt cheap. El Cargador could also buy earplugs !!! : )

 

[El cargador]

I might have a more interesting conversion with the bag of sand than the misses

 

[giardini]

I might have a more interesting conversion with the bag of sand than the misses

Well buy the earplugs anyway then ! : ))