it likely isnt the transmission slipping.. Thats the last gear ever to go out and you would notice slipping in the other gears WAY before reverse.. it really could be almost anything but what fixes the situation is a tune up. usually while in reverse the engine isnt getting enough fuel or spark compared to say driving down a road. the engine has low RPM and that littel bit of stress from an incline or powersteering pump may just be enough to kill a fouled up motor. So if plugs havent been done in awhile and the fuel filter is accessible swap them out. Check the battery and make sure the terminals are clean and the battery has water in it. get the truck up and running right then start looking into larger issues..

Why? A seemingly eternal question on this site by kids with vehicles. What is the purpose of asking why? Just like writing proper names such as Silverado must be capitalized, and yet, kids do not, there are rules or protocol when vehicles are not working correctly. Asking why the washer is not washing is futile, inane and a waste of time. Guessing, even from a reported mechanic, is worthless for you are not a mechanic. The basic rule of car repairs is to take the vehicle to a mechanic for a proper diagnosis and repair. Chevrolet Silverado. A rather large truck. Why is a sixteen year old driving a truck for? To have a $400 a month fuel bill? No one here, nor you, can repair a vehicle. THE standard advise is to go find a mechanic.

if transmission is slipping ..the engine would rev and just sit there ...more than likely ..a motor mount ,,,on passenger side so engine lifts up,,, just reverse and pulls on wiring or a vacuum hose causing a leak causing it to die,, if dieing just off idle clean throttle body ,,,also air idle control valve

Transmission slipping

Every time I back from a parking spot or back into one my truck dies. It starts right back up, put in reverse again, little gas, dies. It has happened once while coasting in drive (giving little gas). Please help. Thanks