Tahoe Rear ended, Hitch Receiver, Frame, DriveTrain

My 2001 Chevy Tahoe 4x4 was rear ended. My tow hitch receiver took most of the impact. The R side of bumper is pushed in (leaving the gap btw bumper n truck to be approx an inch). L side of bumper has shifted away from the body of the truck (leaving a significantly bigger gap btw bumper n body of truck). L side of bumper also droops slightly lower than R side. Does that suggest frame damage? Also, Svc 4 wheel drive light came on after the collision. Does that mean there is a prob w my differential or powertrain or transfer case?

Welcome to the neighborhood!

Let's see some pictures. But, more often than not the bumper mounts themselves will bend in a collision without hurting the frame. But it all depends on how hard you were hit really. As for the service 4x4 warning light, try going to autozone and useing their scanner to scan the trouble code for it and see if they can clear the codes so that the light stays out. It is possible that something got jarred enough to make the light come on but didn't leave any permanent damage.