My van won't shift when it's cold, but once it
As far as back flushing goes, that for a radiator/cooling system . The reason I asked about the fluid type and brand is because I have heard of quite a few instances where another brand of ATF3 or4 was used, and same problem occurred, and when they drained the system, and added only Mopar brand ATF3 or4 instead, the problem went away. I'm told by some Chrysler technicians that Mopar fluid has additives that none of the others have in them, that specifically are designed for Chrysler/Dodge transmissions. Other non-Chrysler mechanics will probably argue that, but in my area, the most reputable garages, will use noting but Mopar fluids in Chrysler/Dodge transmissions. Currently they recommend MoparATF4 in Chrysler products. Cost is a little more, but recommended to last lifetime of transmission as well. Whether you decide to try it, is up to you, but if it were me, and I'm not getting any trouble codes to tell me otherwise from transmission, then I'd replace fluid with the mopar ATF4. Might want to have coolant temperature checked as well, if transmission cooled through radiator, and if not, maybe try blocking off external transmission cooler when cold, to see if it helps warm fluid up. Just be real sure to take it out before it gets too warm. You also might want to inquire if transmission places know of a thermostatically controlled valve in cooler to help overcome that. I know they had them years back, as I had one installed on a Caravan, but I'm not sure if they still do.