Shogun 3.2 DID Stripped Gearbox Mainshaft

[whiteryno111]

Hi, this car (2001 5-spd Manual) has been having this recurring problem since almost new and within warranty, the original gearbox was repaired at a mitsubishi garage the first time after losing drive, took the gearbox apart and the main shaft, input and output splines were all worn out. Replaced those with new original parts, after several years without issues, last year suddenly lost drive again, after some 70k miles. A complete used gearbox was installed and now this one even lasted less, not even 5k miles, took it apart and it's the same thing with the main shaft, splines wear out. Is anyone aware of this issue? What could be causing this? After it was fixed there were no strange noises anywhere, could it be a defect from the car itself?

Thank you
Cheers