Chevrolet Repair: 1996 Chevrolet Cheyenne 4x4 surging at about 50 mph, chevrolet cheyenne, torque converter

Question
I have a 1996 Chevrolet Cheyenne 4x4 with a 5.0 Vortec that surges at about fifty miles per hour slower or faster the surging stops.  It kind of feels like it is trying to shift but doesn't.  It should not be shifting there anyway.  I am not sure if it is the motor surging or the transmission.  There are no lights on to indicate a problem so I do not think a computer will diagnose this.  Any ideas what will cause this?  Thanks for your time and help!

Answer
honestly, i think this sounds like a trans question, only becuase its speed related, not rpm related. see, at 50 youre taching like what, 1800 rpm or so, and you hit that in almost every gear, but the problem doesnt happen till you hit final drive.im not too sure, and my best guess would be just that, a guess. at any rate, for whatever good it will do, sounds like you have a torque converter lockup problem. if you want, check that out. good luck, and im sorry i cant help you more.