ZF 12m noise on engaging

[vic008]

New install of Vetus M3 29 with a zf 12M gearbox. But engage forrd or reverse there is a noise like a crack, or snap from gearbox as it engages gear. Have disconnected shaft and no difference. Any ideas please?
Otherwise running beautifully.

 

[Slipstream 34]

We have the smaller ZF10m. It has a definite and reassuring "clunk" when engaging fwd and rev. I think this is normal. Your cracking sound maybe because it's new. This thread may be of interest.

Hurth Gear box noisy when changing gear

 

[Goldie]

I’ve had 3 Hurth/ZF (who took over Hurth I believe) gearboxes on different boats. They certainly go in with a ‘clunk’ but an engineer told me that the time to worry is if they don’t!