Hello and please help

Hello, my name is Chris, i have a 300 tdi 90 and my new toy a 1980's range rover based trialer. Now I've got the hellos out of the way can i beg for help? I am having problems with my new toy, it's a 3.5 v8 auto, I drove it for around 10 minutes and now it can't find any gears, please help.

Thanks in advance

Chris