Jumps out of high range

[Mr jam]

Hi

I have a 1980 atc 110 that I have owned for many years, but I have an issue with high range..
I have changed the complete sub transmission twice but to no avail

I have made sure she is properly located into high range but as soon as she's under load she pops out into the 'mid position' between high & low
any help would be much appreciated
all gears work well in low range and the clutch seems fine

Thanks

[shortline10]

Are you sure the ball and spring that holds the shift fork from moving are their and installed correctly ? The shift fork shaft can be installed backwards and show your symptoms .
Could also be a bent sub tranny shift fork or the related gears are worn and not meshing correctly .
Their are differences in years on the sub tranny so possibly wrong set of gears ?

[Gabriel]

Yeah, sounds like the detent on the shift drum is bad or missing.

[Mr jam]

Yeah, sounds like the detent on the shift drum is bad or missing.

Cheers for the advice
I will double check the sub trans and let you know the outcome