My 2001 Dakota with 5.9L Magnum 4WD Automatic is shifting way too soon. It shifts so fast I can't get any speed built up because it is bogging down from being too high of a gear. Now normally this thing would take off like a rocket, but it just started this. I cut one of the trans cooler lines about six months ago by accident so it does leak a little but it takes a while before it gets low. I checked the fluid and it was low but once I filled it up the problem is still there. I live in west Texas and you kind of need to be able to build some speed pretty fast if you want to drive here. I saw something about resetting the transmission control module and I tried disconnecting the battery cable and turning the key to the start position and holding it there for 20 seconds but it did not help. I did have a vehicle that did this once and it turned out to be a clogged catalytic converter, but it would not even rev up. I can sit in park and rev the engine, it is just when I try to accelerate that the problem happens. It is already in overdrive before I reach 20 mph. Anyone else ever have this problem? Thanks in advance for any advice.