Ty,,,so you`re moving the stick in approx the right direction & the right amount of movement,,,but it doesn`t actually engage the gears in the box???
or is it that the stick won`t actually move into the positions needed to effect sellectment of each gear?
do you understand what i`m getting at there???
cause quite often people do (as someone has allready pointed out) fit the coupling, shaft & gear stick the wrong way round/up, so the ball on the end of the stick isn`t actually running in the alloy "eye" inside the shifter housing the way that it`s supposed to
easy to fix,,,push roll pin out of coupling,,,remove gear stick, swing rod with coupling around 180deg & re-fit pin & stick, problem solved
sometimes people fit an exhaust retaining bolt to the diff side cover way too long & it passes thru the housing & out the other side & fouls on the shifter coupling, easy fix too,,,remove & fit shorter bolt
I`ve also come across what would seem to be a gear engagement problem,, when in fact it was simply a stripped drive flange at the wheel assy
keep looking mate, hope it`s not internal,
chin up mate