[stover555]

I know this may sound simple, but have you checked the trans fluid? The next thing would be a trans filter repacement. Usually if your trans is slipping it would be second gear, not drive. Have you tried all the other gears, 1st, 2nd.... The reason I say checking the trans fluid, is that when you put the car in reverse, it directs the fluid to a different circut in the trans, and then if you have a clogged filter, it could take a while for the fluid to be re-directed.
I hope this helps.
Mark