Not intending to insult you but make sure it's up on trans fluid! My old Blazer TC was shifting in and out when it was quite low. The transmission leak had gotten worse and I didn't know just how bad. I realize my 700R4 doesn't have the computer stuff that yours does so I don't have the check engine light.
Mark Chapman DP member #653;
1983 K2500 6.2 Suburban, 4" lift, 35" tires, ATS turbo, Banks exhaust/intake, pyrometer, tachometer;
1986 K5 6.2 Blazer, 2" lift, 33" tires, Banks intake, pyrometer, tachometer
1963 wife, one owner, average mileage for the age but in excellent shape, a keeper
1992 daughter, low mileage, pretty, limited edition, but requires some money to maintain
1995 son, sports model, very fast & peppy, time will tell on durability and maintenance costs
"Grease is good"