pulling a 5th wheel up hill on 2003 Ford F-250 Super Duty

this diesel is great until we hook up the 5th wheel and pullup a mountain, we lose power and hear a grinding noise in the front of the hood by the fire wall, also it happen at 65mph, up steep hills too. new turbo hoses. 53,000 miles

Whereas there are dozens of things to be aware of with this engine, focusing on your symptom, I'm wondering if the fan clutch is sticking on unnecessarily. The fan clutches in the early 6.0L equipped trucks could fail.
We had the truck into a diesel garage and had the white smoke problem fixed it close to $2000. The computer said all was fine . Pull trailer to smokey mountain the noise was back ,loss of power, Same problem ,new hose, check it out on computer all is fine.We will check it out again. Thank you,shel
Hang on - another thought...

Did the turbocharger itself get repaired? I would have your turbo checked for a seized Center Housing Rotating Assembly (CHRA), and/or sticking turbo vanes from coking. If there is anything jammed up in the turbo, you will have a loss of power and you will also have abnormal noises.

If you have it checked and find out this is the case, report back here, and I'll give you some more insight on things to be sure of in the repair process.