This is for Dodge - right from the owner's manual.
• Do not tow a trailer at all during the first 500 miles
(805 km) the new vehicle is driven. The engine,
axle or other parts could be damaged.
• Then, during the first 500 miles (805 km) that a
trailer is towed, do not drive over 50 mph
(80 km/h) and do not make starts at full throttle.
This helps the engine and other parts of the
vehicle wear in at the heavier loads.