Foton Tunland 4x4 Clutch Gearbox problems

[Ronwill]

I have a 2016 Foton Tunland 4x4 diesel and 2nd gear keeps crunching, only 48000km on the clock. I have tried different gearbox oils, but still having the same issue. As the clutch is self adjusting, I have tried adjusting the master cylinder threaded pushrod out, but it doesnt make a difference (it only seems to move the clutch bit point up or down). I have replaced the slave cyclinder (which looked fine and wasnt leaking & I have bleed the line, so no air in system but still same issue as before. Now there is a helicopter noise in neutral with the engine running,,when you push in the clutch to the floor, the noise disappears, but when you engage the clutch (pedal out) it comes back again. Any ideas on whether this is a clutch or gearbox issue. Any thoughts appreciated as Iam pulling my hair out with trying to fix this.

[Gordon84]

I have o/hauled 2 of these g/boxes lately, biggest problem is wear in the Chinese main front and rear mainshaft bearings,also bottom layshaft bearings, apart from those problems theyy are a strong box, the same box that is used in some Jeep products,they are a New version NVP 3550