Recently got this minivan. After the van is warmed-up (say 20 minutes highway driving) the transmission having hard time to shift from 1 to 2. I need to let the gas off around 2.5-3K to make the shift and it is harsh. What can be the reason? Do you think should I give a try to Lucas transmission treatment? or any other suggestions?
Thanks.

 

There are no guarantees this will cure the problem, but not knowing the maintenance history of your vehicle, sometimes a fluid and filter change , not a flush,helps.