4l80E dropping out of gear
 

I have a 2001 Silverado 2500HD with a 4l80E transmission. Recently I have been having an issue with the transmission dropping out of gear when engine braking. The RPMS will drop and I hear a fast clicking sound. If I rev the engine up a bit it goes back into gear. I have had this happen in 2nd-4th gear. Otherwise I have had no issues with the transmission.

Any ideas what might be causing this? Could it be the torque converter?

Any thoughts on this would be greatly appreciated.

Thanks!