2004 Chevrolet Colorado suspension problems

The first and ongoing problem grinding in front left, driver, side wheel area. Many attempts have been made to fix this problem, they started out changing the whole front end, along with alignments, after some adjusting the problem will seem to go away only to return with in 2 months second, tires worn from inside out alignment, new tires, I was told one reason was the truck was dirty. I do not feel this is a reason for tire wear. New tires same problem. Third, truck not engaging when shifted into gear.

This 2004 chevrolet colorado, 2 wheel drive truck has vibration and shimmy at highway speeds. The tires are general ameritrac tr 265/75r/15. The tires have been replaced and road tested per the november 2004 bulletin from general motors. The tires have been replaced 3 times with multiple balances, etc. There is abnormal wear of the tires. Purchase date 9/27/04. Beginning of problem 11/22/04, at about 2300 miles. The problem is ongoing with difficulty controlling the vehicle after the new tires wear in a little bit.