It's not the thrust bearing.
The problem is caused by the high level of torsional oscillation generated by the 3 cyl engine, coupled with a minimal amount of light lubricant present in the transmission. These factors cause the mainshaft and output shaft gears to chatter when unloaded.
Both the non-optimal engine configuration (in terms of primary balance and the number of power strokes per crank revolution) and the transmission's operating conditions are dictated by the seemingly overriding requirement to reduce emissions. Proper product development could and certainly should eliminate the audibility of this noise - but as usual, VAG have placed this power unit on the market with shortcomings which are sometimes apparent to their customers.
As with many of their other recently launched products, my advice would be to choose with very great care. Some customers have found VAG's after-sales attitude to such problems to be not entirely to their liking...
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