Yes the engine temp is another matter. Last year i replaced the radiator, water pump, tru cool 40k cooler, etc. Every since truck runs hot when towing or going up a hill. Not sure where to start on the problem either. I put the trans cooler in front of the Radiator and wonder if that could block air flow. Or Rad just isn't good or water pump is no good either.

 

Did you make the necessary program changes when you added the gear and wheels, etc??
Data logs of this happening?

 

Do you have a wideband?

ive never had mine even get over 210 towing, and i tow wayyy more than the truck is designed to.
and the transmission heating up that much with a trucool 40 is kinda strange also.

Id see what your tuner says.


What kinda hills do yall have out there?
arizona?

 

Computer will pull all your timing at 250 degrees. You should fix that before you **** up your new engine. You may have air in system and fixing your overheating will probably fix the power issue.

 

Only lake worth going to in this state that has hills on the way is Lake Roosevelt. They're pretty steep, but no hill is going to make a 4.8 outshine a 5.3 in a towing contest...

 

I was thinking either its running Lean, or air in the system??

 

Yes sir Lake Roosevelt. All changes were programed. I think it needs to be looked at again. Even when i had the 4.8 it got hot after i made changes to the cooling system. It has been drained a few times and nothing changes... Even when i was going up the hill before it started to get hot it still did not pull hard. I did get the P0171 code which is lean and had it at the dealer the last few days and all they came up with was the dirty MAF.

 

Do you have factory clutch fan or electric fans?

 

Right. What about an external trans cooler, you got one of those? Are you on stock radiator? I never hit 250's on my 5.3 not once.

 

The only thing I can think is either air in the cooling system like was stated. Or your tuner has WAY too much timing in it, causing it to overheat until the computer pulls all of the timing at 250*.

Like tarinitup said. You need to get your cooling issues fixed first, then worry about your power issue, because the PCM pulling your timing would make your motor about as powerful as a go-kart, so they may be related, and you can wreck that new motor.