I think its an adjustment thing but I'm really not sure. I drove my car from seattle back to where I was moving (bout 60 miles from seattle) and on the highway I shifted it into OD. My transmission is a 700R4 with a shift kit, whole shebang, 2400 stall, etc, and a 4th gear vacuum lockup set up (tranny shop put it in, I odn't know how it works). Anyway, on the drive back, when I first shift it into OD it lugs and stays right around 1500-1800 RPM like it always has, but then if I hit the gas a bit more, and it shifts back into third, then let off, it sort of seems like it.....half way shifts back into OD and seems like it has more power in the 4th gear now. Is it in 4th gear and the OD just hasn't locked or how does that work? It feels alot different. If any more explanation is needed, lemme know and thanks in advance.