Intermittent knocking on A4 Avant

[Tanuki]

Driving along today, came down a short incline and needed to brake. After braking all of a sudden a knocking noise from what seems to be the transmission tunnel.

I drove along slowly for a bit and under power the noise went away, but when I pulled up again, the knocking noise returned. Clutch fully depressed, the noise stayed constant, engine at idle.

• Engine runs fine. No rough idle
• Seemed to happen after braking
• Clutch has been operating just fine with no slip
• Gears working fine, changing smoothly, no noises.

Got home and let it sit. Went and had dinner, sat down and got my head straight, went back out and and started the car. Knocking disappeared
Drove it round the block, did some braking, still no knock. Drove home and car quiet and well behaved.

What is going on?

Flywheel? Clutch? Brakes? Driveshaft? (By the way where is the driveshaft(s) on a front drive?)

I thought something to do with brakes maybe, because it happened right after braking, though the knock seems to be in the transmission.

Now it's gone, but I'm obviously concerned there is something ready to go if I don't work it out. I've got it booked into the garage but I'll bet I won't be able to reproduce it for them.

 

[46TheDoctor]

If you look in engine bay between right side of engine and coolant reservoir you will see your lefthand shaft enter the g/box, i have no idea what your fault is but you mentioned that you could not replicate the sound, maybe itll only do it if you get it really hot, go out for a good run and get her hot, sorry i cant be of anymore assistance, i know it sounds daft but check all ya wheelnuts and stuff like that.

 

[Tanuki]

Did a quick check to see if wheel nuts were ok and they are.

I drove out on the motorway just now, got it hot, drove back down the road I went on earlier and a braked in the same spot. Nothing. Everything ok.

Can't reproduce it. No idea.

I looked down at the driveshaft on the left. Nothing to report there.

Everything looks intact. Completely odd.

Perhaps it was the engine...something creating vibration which caused the knocking sound?

 

[46TheDoctor]

Dont know then mate, i cant really be nothin serious then.