Vapoppa
With 550 HP, Im guessing that motor probably has 1,750 foot pounds of torque. That kind of power will cause imperceptable wheel spin, even when towing.
I understand that OTR drivers who have 600 HP engines wear drive tires out twice as fast as normal in mountainous terrain. Even with 40K on the drive tires, they still get imperceptable wheelspin which wears tires out faster.
With 430 HP and 1550 torque, if a driver keeps the boost up, and has no curves or traffic problems, he can tow 20K at the trucks top speed up a 7% grade. Even doing that won't be working the engine hard enough to cause the engine fan to activate, or bring the pyrometer above a rather pedestrian 750 degrees.
There is simply no way to utilize that kind of power towing 20 K. Right now I have a 2000 Volvo which has a 500 HP Detroit with 1,650 torque. I won't get an opportunity to tow with it because the buyer is picking it up this Friday. I think it will tow 20 k up a 7% grade like it was towing a bicycle.
onezman
http://onezman.tripod.com/yourrvhaulercom