Originally Posted by Bobert

Sounds like it might be slipping too much. Before i rebuilt mine, it started slipping more and more until it wouldn't move at all. You should be able to break it loose in gravel just a bit.
47mph does seem a bit high.

I don't know if it would work for an automatic, but to see if your clutch is worn out you can put the front end on a tree, then put it in a higher gear and slowly let out the clutch while giving it more gas.

If the rpms just keep going up, its worn out. if it dies, it's still good.