I've had a tire go bad and make the truck pull. My tire guy says the plys seperate and shift. But, that wouldn't mean every tire would make it go left, some might make it go the other way. What kind of tires? Size, brand, load rating are we talking about here? Has your front end been checked out thoroughly? Not every alignment shop does quality work. Try another shop. I'd still say its something with the tires though... My 3500 did the same after a tire rotation, and I got ******. Then, trying to isolate the problem, I switched the front tires side to side. This caused the truck to pull right. Rotated those two tires to the back, and she is nice and straight again. The tires where kumho's. I'll never buy another set of these POS junkers. They chop very easy and the pull thing really don't help none. It's a shame to, cause they have some great traction... Anyway, thats my 2 cents, abe