Tundra AC/Heater blower unit

I am still experiencing AC/heater blower problems from my 2003 V8 Toyota Tundra Limited with 55k miles on it. It has been an excellent truck except now I am experiencing a problem with the volume of air that comes through the dash vents. It seems that even when I turn the dial to the highest setting it just does not blow as fast as it used to and somtimes does not work at all. I noticed that if I smack the blower motor under the passengers side dash it will change speeds and blow faster. I pulled it out from under the dash, it was so easy, only three bolds, Everything looked fine and clean. Now I am wondering…Since that part comes out so easily did Toyota expect problems with that blower assembly therefore not covering it up and making it an easy access? Does it need to be lubicated? Any one else out there have this problem with their Tundra? Would changing out the blower motor take care of of the inconsistencies? Thanks.