Join Date: Aug 2017
Location: North Georgia, USA
Racer-X is offline
Re: Shifting and overdrive problem
A few things. The 2003's had "tow/haul mode." Did you trip that somehow? There will be an amber light on the dash. On the full sized trucks, it looks like a trailer. Not sure what it looks like on the S series. That mode disables the Torque Converter Clutch and changes the shift strategy to use lower gears longer.
Also, if your thermostat is sticking open and the thing is running too cool (or if someone put a lower than stock thermostat in the engine), it won't lock the torque converter clutch until the engine is fully warmed up. With a stuck open thermostat, it may never activate the TCC.
If you can't light up the tires in the first three gears, you need more power.
If you can light up the tires in the first three gears, you need better tires.