My friend asked me to help with his racing trailer, as his truck broke down. I have never tow anything big ever. So it's like 30' + trailer, inside racing car, tools and many different equipment. My guess around 5,000 to 6,000 lbs. I don't have electrical brake control, but it was not far to drive just about 15 miles. So I noticed when truck is on tow mode, it will brake with engine. it was doing fine on good grade hills. And we connect the trail on hitch, the rear of truck went down, and pump came one, was running for 1-2 level a truck and shut off, when we came to our destination, pump was not running and truck was level, after unhooked it pump start running again with little different noise and rear went down and leveled again. I think it was a good test for my rear suspension parts.