700R4 4L60E No Reverse.
Start your car put the transmission in Reverse and nothing happens. It was fine earlier. What happened? If you were to drive the vehicle forward, you may also notice that you no longer have second or fourth. This can be confirmed because your shift from first to third will be late totally skipping second and there will be no shift to fourth. The most likely culprit, a broken or stipped out sunshell This is a very common problem with this transmission and the repair unfortunately is to remove the transmission and disassemble it. Depending on mileage you will probably want to rebuild the transmission at this point so you are also going to need a 700R4 Rebuild Kit  or 4L60E Rebuild Kit The sunshell I referenced is called "The Beast". It is the heavy duty version and will last for years without any problems