Falcon banging into 6th gear

I wrote to you earlier this year concerning my BF Falcon Mk II XR6T and the ZF auto banging into sixth gear and it was suggested there was a revised valve body for the auto that would help the problem, but I now read about problems with the diff bushes that could be the cause of the problem. Since my last letter, I had an independent Falcon specialist check my car and they said straight away that it was my rear bushes and possibly also play in my diff. At the moment I am waiting to hear back from Ford relating to my latest findings! Would the revised valve body fix the problem, or could it be the rear bushes? Any help on this ongoing problem would be great