About 7 months ago I posted a thread about there possibly being a 4 speed that shifts firm. Well I think I found out why my dads 05 magnum sxt with the 4 speeds shifts extremely hard and my 09 charger sxt didnt. Yesterday I changed out my manifolds for the jba headers and after I finished installing them and started my car I guess i ruined the o2 sensors on the headers because they were throwing codes.... I took my car for a test drive and it reacts just like my dads magnum... whiplash from 1-2 gear 2-3 and even a little going into 4th a WOT. It never did it till my o2 sensors stopped working, and my dads never acted like it either till his o2 sensors went out.... doesnt make sense to me that if an 02 sensor stops working it would make the trannys shift like that, but i mist say.... i love it! so if anyone has had this happen before please let me know.