Need to hold gear selector when selecting R or G

[Winchweight]

I can easily select the gear, but need to maintain slight pressure on the gearstick until I have revs applied and the van is moving, otherwise it jumps out of gear. once its in gear and Im moving, its fine.

I guess its a case of adjusting the selector pins? But how?

[Aidan]

if the other gears engage ok then there is nothing to adjust but I'd be checking the condition of the cup and ball and the boot joining them and the general condition of the gearlinkage bushes etc.. and in a new to you vehicle depending on the history doing an oil change on the transmission to see what the drain plug magnets have to tell

[Winchweight]

Is it a simple task to change the cup and ball etc?

The van is new to us, so I guess dropping the oil would be a good idea.

[CovKid]

And as we always remind everyone, ALWAYS ALWAYS make sure you can remove filler plug BEFORE emtying out the old oil. Cup and ball easy - you'll see it on the side of the gearbox where the linkage ends. If its a poor fit, a new ball/bracket will usually sort it.