The brief
The A3 had developed vibration through the cabin and a clunk from the engine bay, worst on pulling away and on gear changes, the signs that the drivetrain mounts have had it. He brought it in. On a transverse-engined A3 the drivetrain sits on three mounts: the engine mount and the transmission mount up top taking the weight, and the pendulum mount, also called the dogbone, down low resisting the engine rocking under torque. As the rubber in any of them ages it sags and cracks, and the pendulum mount especially takes a hammering, so the drivetrain moves around more than it's meant to: the vibration comes through, the engine note climbs, and the slack lets it clunk against its stops on take-up. When they've gone, you do all three as a set, so they needed changing together.
The diagnosis
On the lift each mount got a pry-test. The engine mount and the transmission mount had sunk with cracked rubber, and the pendulum mount, the dogbone, had its rubber bushing worn and split, the play obvious under load, which is exactly the clunk on take-up. All three were tired at the same time. When they go together like that, you do them as a set, fitting one fresh mount next to a worn one just loads the new one harder, so the call was the full set, all three.
The work
The engine and gearbox were taken onto transmission jacks to take their weight, and each tired mount came off in turn, the engine mount, the transmission mount, and the pendulum mount underneath. New genuine Audi-spec mounts went in across the set, every fastener torqued to the manual figures. With everything bolted up, the drivetrain was checked to be sitting square in the bay before the engine was let down to load onto the fresh mounts. A road test confirmed the vibration and the clunk were gone.
The outcome
Smooth at idle, smooth pull-away with no clunk, no clatter on shifts or over bumps, no vibration through the cabin, and the engine note back to normal. The A3 went home with the drivetrain held properly again. Engine, transmission and pendulum mounts wear as a set and they take the rest of the drivetrain's refinement down with them, so doing all three together resets the lot rather than chasing the next worn one a few months later.
