My original owner 2002 Toyota Tundra Truck was being backed up in reverse with a utility trailer attached up a very, very moderate incline on a driveway pushing the trailer onto a gravel pad ALONGSIDE (parallel) the driveway. As it started to spin gravel the truck was put into a 4 wheel Drive LOW RANGE. This is in keeping with the TOYOTA owners manual publication 0M34417U Part Number 01999-34417 Print date 02-0109-01. We followed the manual instruction on 4 WD operation. Within a few feet the truck stopped as if the wheels had hit a curb and there was no further movement no matter the accelerator pedal position and the engine speed was unchanged as if it was in a stall. All of a sudden there was a loud bang underneath the truck and the truck raced rearward 8-10 feet jackknifing the trailer into a tree and upending the truck and trailer. We contacted Toyota on the incident and they had a third party look at the truck for brake condition, floor mat placement and throttle freedom at the body shop & Toyota closed the complaint file. Toyota IGNORED the circumstances and description of the incident in closing the complaint. We have been a very long time TOYOTA truck family and have owned SIX Toyota 4 wheel drives plus a Lexus all-wheel drive. In doing our own evaluation and investigation we have found that the truck went into a 4-wheel drive "wind-up" or "bind" and found information related on it from ASE Certification sites. NO MENTION of this potential issue is pr