2001 Other Ford Models Front end squeal

I have a 2001 Ford F-450, it has recently developed an intermediate "squeal" from the front end. It only happens when going over bump and it seems the slighter the bump the more prevelant the squeal which will only last up to 3 seconds. This does not occure on every bump though as I can drive it for 20 miles without the squeal occuring and then it may occure 3 times in the next miles. I have recently replaced both hub bearing assemblies and the breaks within the last 5 months. I have been under the truck several times and cannot find anything loose or any rub marks. Any suggestions would be appreciated.
Thanks,
Ron