Found the strainer, it was dirty and had specks of aluminium in amongst the dirt, cleaned it out and replaced it.

The transmission fluid was black, although obvious it had been red at some time, re-filled the transmission but the machine still wont move.

I hopeful it's the system that needs priming, can anyone tell me a way to do that with this particular truck

Thank you so much for the reply, I'll have a look for that filter (already got the parts manual so should be able to find it).

I removed the inspection plate at the top of the bellhousing and there is a thin plate held in place by three 17mm bolts, two were loose, the other is missing, any idea what that plate is for ?.

Check the strainer filter in the bottom of the transmission, they block and cause bell housing to fill with oil