WARNING: This page is about a different car, the 2007 GMC Yukon XL and 2007 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.
Inadequate Lubrication at Low Line or Heavy Loads
Checks
Cause
Converter Limit Valve (214)
Valve is stuck closed by sediment or by a collapsed valve bore.