1998 Dakota, 3.9 auto, 126,000 miles...truck runs fine at idle or in park. put in gear, fine until about 2200 rpm. downshifts and no matter how much you fuel/rpm, will not upshift. let off gas , get rpms below 2200, will upshift. I can actually (eventually) get it up to about 60MPH. NO CODES. Took it to dealer, ($200)they had no idea either... Any Ideas??