So I've had this issue for a few weeks now. When my truck shifts into o/d it kind of stumbles. Best way to describe: if you've ever been in any sport and you're tired from running and trip over your legs but catch your step. That's kind of what it does, (except it doesn't have legs). I have a dp tuner and it shifts fine in the 60 or 80 setting. It only stumbles in the stock setting. Is this a tranny issue or something under the motor getting weak?