1997 Chevy Tahoe V8 Four Wheel Drive Automatic 147000 miles
97 2 door tahoe 5.7L; Truck began to decelerate on freeway and would not go over 40 mph. Knocking sound heard from under vehicle. Rpms went up, while speed contined to decline. However, a few minutes later, everything seemed to be working fine, and truck accelerated with no problem. Checked transmission fluid, and everything looks okay. What could be the problem?