4eat wont go into reverese?

[svxsubaru1]

I have a friend with a 91 legacy awd 4eat and it wont ingage in reveres, you can feel the car tring to go reveres, but the trannie just slips in the rest of the gears. Is there any adjustment or any thing else that would cause this. I know the SVX croud has the most experiance with the 4eat so thats why i posted it here.