Transmission problem

[milterino]

Have a 76 450sel with automatic transmission which has reverse problems. When cold and in reverse it sits there for perhaps 7 seconds before responding and backing up. When warmed up it operates normally except when under a load, say backing up an incline. Then it tends to chatter. Is the reverse system connected with any other of the gears i.e. am I going to have trouble in any of the other gears. A trans man says the fluid does not smell bad. Any ideas on what is wrong? Is it out of the question to try and fix it myself? The only man recommended around here (N.W. Arkansas) doesn't want to do it and a guy who will do it I wonder if I want him to do it. Milterino.