1978 falcon automatic transmission

[vk3kbr]

My old 1978 'Henry' has lost the reverse in the auto transmission.
Naturally no manual at hand, can someone direct me to a website where I might get the details of this box.

Seems there are many manuals for sale, however, I would like to download something (even at a price) to have the details required to get 'Henry' back on the road quickly.

The fault occurred while backing out of a parking bay. Two loud bangs then no reverse. Goes quite well forward.

We removed the pan and the fluid was clean with no metal fragments hanging around. The transmition looks fine with aparent damage to any of the vissible components, but I don't realy know what to look for? Any ideas?

Thanks Rod.