Torque Converter Clutch (TCC) Cycling/Shuddering/Chattering
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2003 Mazda B4000, 2003 Mazda B3000, 2003 Mazda B2300, 2002 Mazda B4000, and 2002 Mazda B3000. However, it is still accessible from the selected car via links, so may be relevant.
Check the following: fluid condition, valve body (TCC solenoid, converter clutch control valve, or thermostat by-pass valve/cooler limit valve stuck or damaged), incorrectly tightened valve body bolts (cross-leaks), pump assembly, or TCC assembly (end-play clearance excessive, internal leakage or clutch material damage).