I have a 2005 Ram 1500 4.7 V8. 68k mileage. I have contacted dodge and multiple sources to confirm my towing capacity is 6150 lbs. camper I'm towing is 5000 lbs. runs fine on flat grade or small hill, but steeper hills the truck loses a ton of power, down to about 20mph, and the engine will overheat. If I floor it that doesn't help, and the tach will go up to 5.
I have a transmission cooler installed.
I flushed the radiator and put in a new thermostat - same result.
I have taken the truck to multiple places even to Dodge dealer and they can't find anything wrong with the transmission or engine and aren't getting any codes when computer testing.
Catalytic converter?

 

Maybe plugged cat, if the cat is bad, normally a dtc code would be recorded. Might try checking compression first. Engine shouldn't be overheating at all, and the 4.7 is a very sensitive engine concerning overheating-----it can lead to serious head issues and more!
If it hasn't one---a full tune up is definitely in order.

 

You should shift from overdrive (off) when pulling hills.Engine lug and causing overheating bad for motor.Just a thought.........

 

How about some info about your truck first. What size tires are you running? If you have larger than stock tires that could be part of your problem. Any other modifications? And yes cruzer55 is correct you should ALWAYS turn overdrive off when going up hills no matter how small. If you read your owners manual it says to turn it off anytime you tow. Or if you have a tow mode you should have your truck in that mode anytime you're towing.

 

Also whats your rear end gearing? Does the trailer have brakes? What's the grade? When towing uphill with a less than ideal rig, move to the right and allow the truck to slow a bit. You dont need to haul *** up a hill in a 4.7 with 5klbs off the back.

 

My bet is it's under geared for that much weight. I'm betting 3.55 gears are in the pumpkin. A change to 3.92 or even better yet 4.10 would make a huge difference.

Also, if you are running tires larger than stock, your effective gearing would be considerably lower than 3.55...

 

FWIW, my 2002 4.7 Durango (4wd/3.55 gear) struggled a bit on the long or steep grades with only a 3200 lb. boat with single axle trailer. Dodge rates it at 4300 lbs. max tow cap.
The same vehicle with a 3.92 gear rates 5600 lb. cap.

Interesting the chart shows almost identical caps. with either gear for your 2005 model truck.

 

Your transmission sounds like your slipping if your revving 5 grand and your not moving.check your torqconverter isn't slipping not the trans it self this will smoke your engine and transmission.

 

need to know more about your truck. have you checked the fuel pump and so forth the list goes on. maybe a bad injector have you checked your air filter seems silly but ive seen it get past by the best or vacuum leak look for under the truck if its a 4X4