noticed a leak coming from the gearbox on my 2008 hst 3.6 and gear changes got notchy.

I know this has been done to death bt searching brought up no problem that I had,

removed the under trays
removed the exhaust that sweeps round to turbo
removed the drivers engine mount bolts nearly impossible to get the front bolt hat to remove the gearbox oil cooler
removed the cross member that holds the gearbox/centre diff mount
with gearbox jack stand and a accrow stand I could only get the whole lot up 1" I even dropped the ramp until it was dangerous there was still not enough room for the plastic filter spout to go up. in the end with it been plastic it flexed and went in.

anyone tell me where I've went wrong

I used two jacks. Both jacks at motor mount and transmission need to be lifted.

I dropped the whole car onto to stands under engine and box they wouldn't go high enough

this is what I do.. Rise truck to the highest off-road position, place 4 jack stands on truck frame, after cross member removed, and undo right side motor mount bolt. Lift up (slowly) both jacks. My motor shifted about 1/4", I have to pry the motor to be alignment with motor mount and bolt hole.