I thought there was a TSB on this on Fritz's site. The TSB I'm thinking of talks about the truck going left or right when not under control of the driver. There is one in there but it looks like it has been corrupted by the 5th gear nut problem. Anyway, if the allignment has been done you may have the brake caliper not releasing on the right side. You could check or have the dealer check for unusual wear on that side. You may want to do a search on this topic. This is not a new phenomenon and there should be some ideas that you can take to the dealer.
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2001 HO 6 spd 2500, 4. 10 LSD, Towing Package, Electric Brakes, SPA EGT/Boost Gauges, Fog Lights, Real Backup Lights, Molded Running Boards