2003 Tahoe.. Fine at idle.. overheats when driving a mile down the road.. Replaced thermostat and checked for any leaks from hoses water pump etc but still cant figure out why it overheats.. Does take red antifreeze and i did put some that says can mix with any color but don't think that is the issue. Help would be great.

Re-flush the system again, I know but it's best you do. Buy a lower degree thermostat and see how it does.

Not sure I follow your wording on the different temps. If the system is full of coolant and working correctly, the thermostat should open at 195 degrees which would be several miles down the road. Once the thermostat opens both radiator hoses should be warm. If the water pump is not working the engine will get hot very quickly.
Have you tried running without the thermostat to see what happens ?

Have you checked the fan? A bad fan either electric or manual with clutch will cause a heating problem.

It is more than likely your water pump. Can you run it in park with the radiator cap off. The cap on the radiator not the overflow tank. When the temp opens the thermostat you should see flow if the pump is good no flow it is probably bad. If you don't see flow check the upper hose for temp and the lower hose. If the upper line is barely warm and the lower hose is significantly hotter, it is either water pump or thermostat, but since you replaced the thermostat I would be back to water pump. BTW you should use either a contact thermometer or an infrared to check hoses, although it was done by hand in the old days.

what makes you think it overheats.
the guage only?
or boiling over.

is A/C on or off, at over heat, assuming it really is???

if it was a head gasket it would overheat long before 20-30 miles if there is no sign of water leaking from hoses etc when the car has warmed up it is most probably the radiator or possibly the water pump or thermostat has called it a day

your heater has apparently restricted the coolant flow....hopefully a good system back flushing will cure the problem....use a flush obtained from a parts house....I would buy the hose kit for flushing as well...good luck to you

Presurize system with radiator cap on to see if you are holding 10 to 13 LB pressure as high as 17 LB. Get new radiator cap for your radiator. Check for a slow leak at pump hose thermostat conection , is it wet ?
Do you have a Summer Thermostat ?
Vitally

have the cooling system purged of air (air release bleeder valve on top of thermostat housing) loosen do not take out let air out tighten back

Hello,i would replace the thermostat first.Check for water leaking around water pump,listen to hear if water pump bearing is shot and see if you can wiggle the water pump pully.if you can.bearing likely bad.,,hope this helps