I don't know if the clunking or "slop" is normal, or caused perhaps by
less-than-good-quality parts. I had the same problem (minus the dog) hauling
at 6x12 utility trailer using a 6" drop hitch in my receiver. I also don't
know if it's recommended or not, but here's what I did to eliminate the
slack:

Run two beads of weld on each of two adjoining sides of the hitch box.
Patiently (with file or grinder) remove enough of the weld from both front
and rear of both sides to achieve a good fit. I ran beads which did not
extend into the radiused portion of the hitch box and were approximately
1/4" to 3/8" in width. One set was about 1" from the front end, the other
about 1/2 to 1" from the end of where it rests in the receiver.

Initially I was concerned that a tighter fit would cause binding problems if
I chose to remove the hitch, but I think any substantial trailer load
eventually wears the weld beads and/or inside of the receiver enough that
this was not a problem.

For the record, my receiver and frame is also a "Reese" unit. The drop hitch
was purchased locally at a Tractor Supply store. Hope this helps (or at
least solicits some interesting responses...).

"Spencer" wrote in message
m...
My wife and I would eventually like to get a boat which would
inevitably involve trailering. The problem with this scheme happens
to be our dog. A few months ago, we pulled a trailer (with decent
loading at the hitch) with our SUV and Reese hitch (square socket
receiver). When there were bumps or speed changes, the clunks just
drove our dog wild who was in the back of the SUV. We'd like to
prevent that kind of trauma again if we were to pull a trailer. Does
anyone have any tips as to how to prevent the clunking? I'm not sure
if the clunking was primarily coming from the receiver hitch or the
ball/trailer connection, but since we had good loading on the ball,
I'm guessing it was the receiver. Anyone else had the clunking
problem? Any solutions? (I was thinking about using some sort of
shims in the receiver, but I'm not sure that would work if we were to
drive several hundred miles...) Thanks!

ps. NOT bringing the dog is certainly one solution, but unacceptable
at this time...