My 99 caravan was running fine, then a week ago I was driving to work and my alternator went dead. I did not realize it until the van started down shifting and really acting strange. ultimately I found out the alternator died and the battery was at only 5 volts. I changed the alternator, charged the battery. Now the van won't go into overdrive. It shifts 1st 2nd and 3rd fine, but if it has to downshift from 3rd to 2nd under power it slams in and sometimes ends stuck in 2nd. When it does stick in second, if I turn the vehicle off, it's fine again,,,, Please What is going on?