I often see sludge in a 1.8T where the driver never uses synthetic oil.
Other than that, I never see any sludging.
Manual trans issues? Not that I know of. The only driveline issue I see is a failure of the RF inner CV joint. A large socket doesn't remove the axle nut, it is either a 30 point socket or a huge allen key, so you might not be able to do this without buying tools.