Slow Idle - Tranny Question

[Zilverado]

Can a low idle (around 400 to 450 rpm – specified normal is 750) condition cause an automatic transmission to temporarily disengage or “slip”?

The engine runs so slow that the vehicle will barely move or not move at all when sitting at a light and foot off the break. Sometimes when shifting the tranny into reverse, it won’t kick into gear until I bring the RPM up, and then it kinda “slams” in. I’ve had the tranny rebuilt before for a similar type of problem (but no idle problem at the time), so I’m just a little nervous now. Or could the slow idle be causing this?

FYI, the engine in question is computer controlled, fuel injected (not my Chevy), and so the idle adjustment is not just a simple turn of the screw.

Any suggestions would be greatly appreciated.

Thanks