2005 Hummer H2 Lost power until engine stop

We are at cruise control (2000 rpm) speed 75 mph going up hill until rpm went up and down from 2000rpm to 4000 rpm and jerking (transmission temperature approximately 210) and start loosing power until the engine stop. Outside temperature is 110 degree Fahrenheit. Turn off AC turn on heater to remove heat and cool down engine.
New engine oil; transmission fluid (used fluid spec) and new brake fluid (flush brake fluid). Cleaned air filter.
Hearing something soft sound scrambling under driving side flooring. While driving.
After cooled down for one (1) hr, engine run and after 12 miles smell burn, stop check hood no smell burn, check transmission fluid (red and on between the mark). Start engine and run 65 mph and runs great and transmission temperature is 200 deg Fahrenheit.
What should I do? And to resolve this problem?