I will start off by saying I am a YouTube mechanic and not a real one! Just picked up a 2005 3.7 dodge dakota that I thought was in great shape (no rust and 150kms). It is an automatic but I noticed it shifted hard from 1st to second but I didn't think twice about it. After a week of driving without issues, I was at a stop sign and when I went to go and it accelerated to 5000 rpms before catching first gear. It did this two more time until I pulled over and saw coolant boiling out of the overflow. I replaced the thermostat and ended up doing the radiator to because the bottom tranny cooling lines were lose. All fluids look good and at the correct level. I was in the process of flushing the radiator and noticed the rad fan turns on right when the truck starts up with no ac, heat, etc on. I don't know if that could be a cause. It also seems to run a little rough at idle (even before the overheating). I went to go for a little drive today hoping it was fixed but the tranny still revs before catching first gear (and reverse). If someone could point me in the right direction that would be great! Thanks.

 

the 3.7 only has a clutch fan which is belt driven. it will spin right away but not quite full speed unless it's needed. if you hold it, it should spin freely without trying to turn the belt. If it doesn't turn at all without trying to move the belt, then the clutch has failed and needs replacement.

unless someone added or replaced it with an e-fan and that's what you are mentioning. if so, then they didn't use a temp sensor.

As for your transmission issue, it sounds like a torque converter issue, not quite a transmission issue. i would start with getting it scanned, and not just a code reader, a real scanner. if you can get some form of live data on it and check what it is telling you when you start moving in first or reverse.