Loud blower motor

I have a rattling like noise when my truck gets to about 2500 RPMs only. Does the blower motor get rusty or something? Or maybe the housing is trying to blow up. Is this normal?

My blower motor made a lot of noise, like rattling. It may have seemed to happen in conjuction with engine rpm when it first started to act up if my memory is correct(long time ago). It was so bad before it died it was a constant noise. While on the subject, I picked up a new motor at Checker for $30something (as apposed to $170 at dealer) and I'm hoping the resistor pack fix will take this time with the new motor in, then it's AC conversion and recharge time - does it ever end..... :repair:

update, blower moter is out - can't figure how to remove the fan from it and slap it on the new one :dunno: well back to work....
Another friday night and I'm working on my Jeep again.....