uneven tire wear on tow PU= '07 Toyota Tacoma 4WD

between front and back. Michelin Defender 17" 245 comes with 12/32" instaled new 9,000 mi. ago (recom. 6-8,000 mi.) At rotation rear @ 7/32", front @ 11/32". Since put on 1,000 miles towing 25, 000 #...