Engine stalls?

When I place my 1999 Dodge Ram truck 5.9 into reverse it sometimes stalls. Normally when in Drive you can take your foot off of the brake and it will just slightly creep forward until you accelerate. This is not the case in reverse. In reverse if the engine doesn't stall immediately, if you were to take your foot off of the brake you would be going 10mph at idle. Why is it only in reverse that it does this? Where do I need to look for the problem. I recently changed the IAC motor because the truck would die when you took your foot off of the accelerator. This corrected that problem, and the truck was driving fine until last night when it started the Reverse thing again. It started it after a hunting trip where I was driving on a gravel road. Could it be a bad connection somewhere? There are no codes in the PCM. The was recently rebuilt, but the govenor pressure solenoid was not replaced, could that be the problem? I am in need of some serious input and solutions. Help!!