I got a scare the other day under my Tahoe. I had it backed up on ramps. Had the front tires blocked with wheel chocks, both of them. I was searching for a noise from the t-case to the back with my girl in the driver's seat power braking it. Not constant but periodic accel and then let off. I had worked my way back under the rear axle with the pumpkin just above my chest. She did a power brake and my G80 worked and both ramps kicked back and both rear tires had gotten to the apex at the top of ramp where it flattens out. If the ramps would have kicked out further and the wheels/tires went down the ramps, I could have had a caved in chest or maybe worse. In hind sight, doing that power braking on the ramps was not smart and if I did, the ramps should have been turned around. Then the tires would have had to jump the tall lip at the top of ramp.
My girl freaked out. She was telling me that she will not allow me to go under a vehicle again. I talked her down but she is not happy. I may have to invest in a set of those lifts that take them up, about 3 feet, and lock in place.