hi guys I had the same problem :
'' transmission will shift down to what appear to be first gear ''
yesterday i had code Po302 on my 2003 dodge minivan and I changed coil pack and my problems were gone. Including transmission shift down.
for few months i had to use 3 shift instead of D shift for driving because of transmission shift down sooner than it supposed to.

 

hello, I was wondering if anyone has had the issue with there transmission that I have. when you put the van in gear, reverse or drive, the speedometer jumps to 20 mph without any motion of the van. it also has a hesitation before it takes off. it doesn't clunk or shift hard while taking off, just delayed.