1997 Tahoe transmission/transfer case

1997 Tahoe 4x4 4 door 5.7 liter (190K)
When shifting to reverse, the vehicle just revs up and stops suddenly. After shifting to Park or Drive and coming back to Reverse it sometimes kicks in but at other times it goes back to stopping suddenly and reving loudly. Going forward is fine with no stalls or slips, but as soon as I put it in reverse, its like rolling dice because it may or may not work.