Thanks for that reply; it sounds a plan - although all forward gears are OK and if reverse is tried after a hard drive forwards it will work for a limited while, I will do an oil change first, here's hoping.

Check and seek advice first! As I said I do not know. But have read of others solving problems.the hard way when an easy solution cured it in the end. Eg the fluid or the even shifter cables.

Post about the problem.in the tech help for guidance and advice first with your symptoms.

Sent from my SM-A600FN using Tapatalk

Although it is a diesel, THIS thread does list a lot of information on testing, and some further reading.

and further reading HERE and HERE.

I always imagine replacement of the reverse piston has potential to introduce other issues. So I would want to exhaust the easier things first.