I don't know if this will help, but here goes...
Fluid levels are vital in autoboxes - way back I had an old Rover P6 that stumbled up the road... attend to the levels and, hey presto, smooth as you like! :clap:
However, if it needs internal tinkering... try Loughran Bros of Towcester for advice (01327 359167)
I know that they have a 'tame' gearbox guru based at or near Silverstone - not (yet) had cause to use his service, but understand that he is a fine fettler...
Like I said, hope this helps
Rob