I'm very happy with the 4spd swap in my TD. No vibration at all, but does have a slight buzz when lugging 3rd/4th gear, not really a vibration though, car is smooth running and nice on highway.

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82 MB 300TD, 87 Audi 4000TQ, 05 Audi A4 avant 1.8T 6spd (Wifes), 63 356C, Samurai VW 1.6TD, 71 NSU 1200C, 71 Toyota Hilux, tractors and junk