1999 Chevy Silverado 1500

For sale is my 1999 Chevy Silverado 1500 Single Cab with metal roof rack. Used it all summer for landscaping work and ran good until transmission issues. Truck starts to slip out of gear once you get past 45 mph. Engine is good. Truck battery is dead right now but would start if jumped. Mileage is about 250,000, an't remember and truck is too dead to check. Auto Transmission. Audio system doesn't really work and truck is a little dirty, t went from work horse to sitting. I have a new O2 sensor for it. Good inspection. Asking $1100 or B/O