this is NOT the bucking problem that Fords had, this is something different and probably not worth worrying about but I thought I'd check.

ONLY when towing our horse trailer... when slowing down say for a light or stop sign or wotever, no foot on the brake, or even the gas, just idling to a stop, the last few feet the truck does this shimmy, almost the same feel as if you have a warped brake rotor, just a slight back and forth (enough to spill your coffee if its full!!!!). not enough to worry the horses, or anything violent like that, just a slow wobble as you coast to a stop. ONLY does it when towing the trailer (four horse featherlite). Is this common? is this a precursor to somethign major? should we be worried. its been in to Ford and they can't figure it out (as per usual. sigh). I've checked all the TSB's and can't find anything that talks about this. anyone else experience this? its going in this weds for some other work to be done and I"m wondering if I should chase the guys up to check this out for me. We are about to take a huge trip across country (1000miles to regina) in three weeks time. I don't really want them messing with the truck unnecessarily, since its running fine and we have NO problems.
just wondering if you've heard of this???
again NOT the commonly known bucking problem. we've never had that. truck is a 2003 but has a 7.3 powerstroke, NOT chipped. stock from factory.

The folks I've talked to with a similar problem where told by Ford service techs that is was driveline angle problem and they added shims. This helped some but didn't totally smooth out. Some of the F450's with this problem were solved by a tracking bar added to the rear axle. But all this is not easy to track down with Ford.