I had a grind/groan noise on take off that would happen at random times. It sounded like it was coming from the left front area behind the dashboard and would go away on its own or if I lifted off the throttle. Sometimes I could hear it as the suspension articulated over bumps and undulations in the road. It always went away before the 1/2 shift as well and never really came back again until the next take off from a stop.

While changing the trans fluid I looked up at the transmission mount and saw it was missing the nut where it meets the crossmember. I put a new nut on and the problem is solved. Its been a little over three months and its perfect. Im finally getting the upper hand on this truck!! Hope this helps someone out.