Originally Posted by tom2112

Well, that is odd that it is only into reverse. If it was all of them getting stiff, I'd say it was low trans fluid or time to change it. But that doesn't go with just reverse being the trouble. So it will take someone who really knows what they're talking about to chime in.

My one last idea:
When you try to put it into reverse, does it help at all to put it into another gear first, then into reverse?