I should get a log with my 2011 Suburban. stock 5.3/mild built 6l80 w/billet converter, tru-cool 40k routed through the radiator cooler.
I see about 30-60 degrees above ambient year round when unloaded. Towing a 6k lb travel trailer I see no higher than 100 above ambient. I only see that when it is full throttle, up a steep grade, converter unlocked and in 3rd or 4th gear, for extended periods of time. Once I top out and it shifts back to 5th and locks the converter back up, it will usually cruise about 170 on the highway in 100 degree temps. No temp spikes when coming to a stop, in fact it usually drops temps fairly quickly when stopped.
I have taken temp readings with an IR gun when the engine is fully warmed up. Reads 210 on the gauge. Reads ~190 at the thermostat, ~170 at the inlet side of the radiator, ~130 at the outlet side of the radiator(where the trans cooler is).
So, if you are pumping 178 degree trans fluid(that's temp IN THE PAN, before it goes through the pump and converter) through the pump and converter, it's probably well over 200 degrees by the time it makes it to the trans cooler in the radiator. The in-radiator cooler is then going to try to pull that down to ~130 to match the engine coolant on that side. Then it goes into the front mount cooler where the ~100 degree air does it's best to cool it down more. You are likely getting a much better heat dissipation from the liquid/liquid interaction with a ~70 degree temp difference than you are from the air/liquid interaction with only 30-70 degree temp difference.
I see about 30-60 degrees above ambient year round when unloaded. Towing a 6k lb travel trailer I see no higher than 100 above ambient. I only see that when it is full throttle, up a steep grade, converter unlocked and in 3rd or 4th gear, for extended periods of time. Once I top out and it shifts back to 5th and locks the converter back up, it will usually cruise about 170 on the highway in 100 degree temps. No temp spikes when coming to a stop, in fact it usually drops temps fairly quickly when stopped.
I have taken temp readings with an IR gun when the engine is fully warmed up. Reads 210 on the gauge. Reads ~190 at the thermostat, ~170 at the inlet side of the radiator, ~130 at the outlet side of the radiator(where the trans cooler is).
So, if you are pumping 178 degree trans fluid(that's temp IN THE PAN, before it goes through the pump and converter) through the pump and converter, it's probably well over 200 degrees by the time it makes it to the trans cooler in the radiator. The in-radiator cooler is then going to try to pull that down to ~130 to match the engine coolant on that side. Then it goes into the front mount cooler where the ~100 degree air does it's best to cool it down more. You are likely getting a much better heat dissipation from the liquid/liquid interaction with a ~70 degree temp difference than you are from the air/liquid interaction with only 30-70 degree temp difference.