The brief
The 528i was vibrating at idle hard enough that the owner could feel it through the seat, there was a clear clunk every time it shifted between Drive and Reverse, and the shifts themselves had started to feel slow, a beat of delay before the gear took up. Three things, one underlying cause: the engine and gearbox no longer being held firmly in place.
The mounts are the rubber-and-fluid blocks that locate the engine and gearbox and soak up their movement. There are three of them here, one each side of the engine and one under the gearbox. When they sag and go soft, the drivetrain shifts around on take-up, which is the clunk and the vibration, and that slack also makes the gear changes feel less crisp than they should.
The diagnosis
On the lift each mount got a pry-test. Both engine mounts had sunk visibly, with cracked rubber on the front one. The gearbox mount was not fully collapsed yet but had measurable movement under load, on its way down.
So two were gone and the third was close behind. Replacing the worst one or two and leaving the rest would just mean coming back in soon, so the right call was to renew the full set, all three mounts, in one visit while the access was open.
The work
The engine and gearbox were taken onto transmission jacks so the weight came off the mounts, then each old mount was removed in turn and a new BMW-spec replacement fitted in its place, all three: both engine mounts and the gearbox mount.
Every fastener was torqued to the manual figures, and before the engine was allowed to settle back onto the fresh mounts the workshop checked the drivetrain was sitting square, so the new rubber would not be loaded crooked from the start.
The outcome
The cabin went smooth at idle, the clunk between Drive and Reverse was gone, the shifts came back to normal timing, and nothing buzzed through the steering any more.
The 528i went home with the engine and gearbox held properly again. For the owner the everyday difference is a car that feels solid and refined rather than shaky and loose. And doing the whole set at once means all three mounts age together from here, instead of a string of return visits as each old one gives out.
