Bert troubles

Guys I need some help. I'm having trouble getting my transmission out of low and into high. I've replaced the shifter fork, the shafts and installed the new piston type deal that replaced the old rubber brake cup. I've adjusted the linkage every way but just throwing them away. Lol
With the engine running sitting at idle I can get it in and out of low very easy but when I start rolling like normal and go to shift it will not move until you just stop.
Any one ever had anything like this happen?

Just had the same problem, my reverse idler gear broke in half. I would also check that it wasn't installed backwards as one side has a lead in on the teeth and the other side doesn't.

I'll check that too . Thanks