I own a 2008 Fourwinds Windsport 36R MH with 13K miles on it. I by chance was looking at the rear axle and took note of the rear sway bar bushings. The passengers side bushing was all but gone and the drivers side wasn't much better. I replace the bushings at $90 and about 1 1/2 hours of my labor. I've attached photos of these parts. In the first picture the left bushing is the drivers side part. I had to cut this bushing to remove it from the sway bar, that's why there's a gash in the top side. The right bushing is the passenger side part. As you can tell there's not mush left of it. In fact the sway bar on that side was rubbing the bushing mounting strap. When I remove this bushing I had to scrape the remaining rubber off the sway bar since it had been bonded to the sway bar from the heat of the bar moving over 13K miles. These parts were the original from the Ford factory. Now I'm not complaining mind you I just thought I'd post this issue I had and maybe others might want to check there bushings. BTW the remaining front and rear bushings on the sway bars are like new. I would have thought that these parts would have lasted much longer but obviously not. I do some towing maybe 50% of those 13K miles so it's hard to believe these bushings became damaged so quickly. I haven't driven the NH since I replace the bushings so I don't know what difference the new parts will make. I'll find out next month since we're going to do some traveling.
For an eleven year old coach you had quiet a lot of bushing left. In 2011 my 2006 coach had empty mounting frames and what looked like black slag. Replaced with blue ploy bushings I got from an eBay seller. At 13 years the fronts still look OK as of last week.