I just purchased a used '92 2h Charmac bumper pull (1 axle).  The dealership installed a brake controller, and things seemed fine on the 40 mile ride home.  When I hooked up the trailer several days later, every time I applied the truck brakes, there was clunking back at the trailer.  This happened going forward and in reverse.  I tried adjusting the brake controller a little, but that didn't seem to make a difference.  The dealership did maintenance work on the trailer for the 2 1/2 yrs the last owner had it.  I am waiting for copies of the records.

Any ideas?

PS - Also, this was a brand new, never used truck tow package. The plug in for the electric was fine the previous night when we used an adapter....but right before I left with the trailer the next day, the tech told me that where my electric on the trailer plugs in  (next to the receiver)was cracked and they wouldn't have the parts to replace it for a week....(I was nervous - 1st trailer purchase....wasn't sure and needed to check with hubby about it being cracked the night before).  Not sure if they also scraped the paint on the bumper - didn't notice that until the next day.  UGH!