WARNING: This page is about a different car, the 2006 GMC Yukon XL, 2006 Chevrolet Suburban, and 2006 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
Transmission Overheats at WOT
Checks
Cause
Converter Limit Valve Bypass Orificed Cup Plug
The plug is blocked, therefore the converter limit valve is stuck closed.