Technical Help needed as off the road - Strange Knocking drive shafts - diagnosis challenge

[beattiedh]

Hello All

Hope you can help.

2011 Twin air and got a strange knocking recently. It sounds like a suspension issue so to start so took the car out and it is indeed knocking but sounds low down and does not seem to be speed related i.e frequency does not change with speed.

Jacked the car up and checked all the suspension components and wheel hubs - all tight and nothing loose. Whilst front was on stands I started the car and into first then second and there is a knocking. I then took the wheels off and ran the engine up again. The passenger side (short drive shaft) span freely whereas the drivers (long shaft ) did not all the time. When I held the passenger side break disk the knocking increased but again did not seem to be speed related.

Turned the car off and then when underneath and turned the shafts by hand and the drivers side did feel stiff.

Is this a drive shaft issue or gearbox/diff issue?

many thanks for any more diagnosis ideas before I start stripping.

Duncan

 

[z rider]

It depends on where the knocking comes from. Does it come from the gearbox (center of the car) or from the hub side?
If center of the car it could be differential or inner cv joint.
If hub side it could be the outer cv joint.
You can try to push the driveshaft in the direction of the gearbox and back several times to settle the cv bearings and then try again.
It's not unusual that only one side spins with wheels up, if one brake sticks a little, the diff will take rotation to the other side.

One final thought: If the hub moves up and down a little when rotating it could also be the stabiliser struts. They are known for knocking sounds that are not speed related

 

[beattiedh]

Thanks for the reply. It is towards the centre so was going to get the driveshaft out and look at the inner cv.

The stabiliser struts (I assume aka droplinks) seem solid but happy to replace them as they are old. Would make life easier to test at least however the knocking was still there when the car was not moving.

 

[John202020]

Open the door and rock the car side to side, at this age most of the suspension is shot if it's not been replaced as the noise is not there stationary nor speed related doubt drive shaft issues.

 

[DaveMcT]

With both front wheels off the ground, it's normal for one wheel to turn while the other stays still. That's the differential putting power to the side with least load (friction). You will sometimes get a chattering noise with is gearbox backlash. Again nothing to worry about.

Noises from under the car - exhaust banging on the floor. Check hangers flexible joint and the clamp just below catalyst outlet. That's especially important to avoid the catalyst getting cracked. While under the car, check the gearbox torque mounting (dog-bone) worn rubbers in there can be noisy.

After that check suspension in detai. Anything bad slight to be noisy should be obvious.

 

[beattiedh]

Thanks Dave

So exhaust is checked and all good, suspension checked and all solid, and knocking is when going i gear so I am removing and inspecting the driver's side driveshaft as it really sounds like it's coming from there. Easy to replace too

 

[beattiedh]

Stripped, gearbox emptied and drive shafts removed. CV's regreased and put back together. knocking gone. Very odd indeed