Hi
Percymon, visually the gearbox, bushings and side plates look in good condition. I have tried complete new interlinked drive shafts from gearbox to wheels with no improvement so i'm guessing the issue is within the gearbox or potentially still a combination of the two.
Rich1978, there is definately a few things to look at on that link and I will concentrate on working my through it to see if this sorts it all out. I've come across a few suggestions for modifications along the way but that list looks very useful.
I had to buy a new battery for it after all these years of no use so am determined to get it running again properly.
Thank you both for your feedback, it's much appreciated