Truck is a 2005 Envoy SLT 4.2, PCM4LESS 87 Octane tune, has a G80 rear diff. When I take off it feels almost like i'm driving across the warning rumblers on the side of the road, or a shudder. Doesn't matter if i'm turning, or going straight. Does it for the first 3-5mph and then goes away. What could this be? The G80 going bad and disengaging and letting go again and again? Transmission shudder for some reason? I assume it's bad, but honestly have no idea, lol. My car before this was a Ford Crown Vic with a ton of mods. And I kinda miss the simplicity of that versus my Envoy, lol. Talk about something that was easy to work on.