I have a 1999 F550 stake bed w/ manual transmission. When towing an 8000 lb trailer up an extended grade (maybe 1/2 mile or more), the temperature climbs to the top of the range. I always get out of it before the gauge gets outside the safe range, but I'm guessing it would peg if I let it.

It also seems like it lacks power in general, and especially when towing. I would think with the low gearing (2300-2400 RPM at 60 MPH), this thing should not even know it's pulling a 4 ton trailer, but I regularly have to drop a gear on anything more than a slight grade, which means I'm under 50 MPH and the loaded semis are passing me!

There are no OBDII codes. I will take it to a stealer if I have to, but I thought I would put it out there for opinions before I sink the cash. Any ideas?

Thanks,
Rich