The gearbox itself is reliable and has two weak points. One is the input shaft bearing, which is short-lived, the other is the oil seals, which leak continuously.
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The leak is the more dangerous one: any drop in the oil level wears the shafts and the gear rims, and that wear cannot be undone. Most versions come with a dual-mass flywheel, which is not the most durable part either.
What to check
- Look at the bottom of the gearbox and where the driveshafts come out: fresh oil means a leak
- Ask when the gearbox oil level was last checked, and ask for the invoice
- At a steady speed, listen for noise: a worn input shaft bearing drones