2004 Chevy Impala Thermostate

Air in the system, low coolant (leaks?), Defective thermostat, cooling system that's starting to clog up a bit, bad water pump.
If you never serviced the cooling system, this is a perfect opportunity to flush it (back flush), replace thermostat, check water pump, and refill with fresh coolant (dexcool). If you need more in depth info on how to do it, let me know.

Hello again,

I just saw your comment; thanks for the vote by the way. The car being out of warranty, I don't think there's much you can do. I'm wondering how come your transmission went out after 89,000. Maybe you have a leak and you got low on transmission fluid? Or your cooler started to leak and you ended up with coolant in your transmission. A " œhard' driving style can take its toll on a transmission as well. I don't know. My wife for instance drives a 03 Impala with 146,000 on it. The transmission is not in the best shape but we got our money out of it. At this point, if you want to get it fixed, your best bet is to call around and do a little bit of research on the transmission shops in your area.
Sorry about your problem; transmissions are really expensive to fix.