As gmw photographics pointed out; definitely not normal. The suspension units on these trailers are the "dry" type, i.e., no points of lubrication for the shackles or equalizers if equipped with dual axles. When new there are either hard coatings on the hanger bolts or nylon type bushings. With age and mileage, the hard coating wears away or the nylon bushings wear through and what you wind up with is dry "soft metal" making contact with the shackle tubes - squeaking. On a 2007 with some miles on it, that's to be expected. Replacement bolts and or bushings are not expensive to buy nor to replace and well worth the time and money if that is the issue. You could even "upgrade" to what are called "wet bolts"...those have a Zerk grease fitting in them and you can periodically hit them with a grease gun and they will last, virtually, forever.