The engine is overheating.
the freeze plugs on the side of the motor could be done.
could be your thermostat or you have no antifreeze coolant or your water pump is going bad
It could be caused by a defective pressure cap on the radiator cooling system.
If it is a vortec engine, it is probably the lower intake manifold gasket. In most cases you can smell it when the engine is hot.
First you have to determine the cause. Could be a faulty thermostat, frozen coolant (insufficient mixture of antifreeze), low on coolant or possibly a bad head gasket.
Look just below the water pump to see if any antifreeze is visible. Water pumps will sometimes leak and drip out antifreeze. Check the engine oil to see if antifreeze is mixed with the oil, indicating a blown head gasket.
It could possibly be the thermostat or the cooling fan. Let the engine warm up and when it gets to 232 to 235 degrees the cooling fan should come on. If not you need to go from there.
Thermostat could be at the tempure setiting, No antiboil antifreeze coolant, and the water leakage or a bad waterpump.
if fans are working and thermostat is good welcome to the world of northstar famous headgasket/faulty headbolt and stripped block crap engine problem
It could be that your heater core is blocked or damaged somehow.
Overheating the engine shouldn't effect the transmission. Overheating the transmission could.