Rolls forward on reverse gear

My 2000 SR5 rolls forward on a down hill slope when I put it in reverse (automatic trans). I know that in a severe slope the engine torque by itself will not be enough to keep it from rolling, but this occurs on even a low slope driveway and I don't even feel resistance. It's like I have it in neutral. When I apply the gas or the brake it's fine, but once I release, it begins to move. My mechanic said it was normal, but I've had it for about ten years and never noticed it until I was trying to hitch up my camper. Any ideas?

 

Never mind. I couldn't duplicate the problem. I hope it doesn't mean my transmission is going out.

 

If there were anything to go out it would be your torque converter.....but that is unlikely. Your tc is what transfers torque into the tranny and acts somewhat like an automatic clutch. Tc's work off of rpm so what it was probably was a period of low rpms due to your a/c kicking on or your fan clutch engaging and your rpms were not high enough to fully engage the torque converter.