Diesel67

Im convinced its not the oil as much as i will change it to the Mopar that most recommend.  I do have a spare solenoid pack i think when i broke my previous voyager (same model) appreciate your advice bud, been driving these for 20 years, just very unlucky with this one. best model was the 1999 v6 petrol , I miss it 
 

Have you had the car long?
Any documented detailed history of service?
Did you use Mopar ATF+4 fluid - the specific type for the transmission on these?
If not, that could be part of the problem.  Or naff all to do with it.
These are very sensitive little souls, on all manner of things....

According to the manual !! 
TRANSMISSION TEMPERATURE SENSOR
The TRS has an integrated thermistor that the PCM/TCM uses to monitor the transmission’s sump temperature. Since fluid temperature
can affect transmission shift quality and convertor lock up, the PCM/TCM requires this information to determine which shift schedule to operate in. The
PCM also monitors this temperature data so it can energize the vehicle cooling fan(s) when a transmission “overheat” condition exists. If the thermistor circuit
fails, the PCM/TCM will revert to calculated oil temperature usage.
CALCULATED TEMPERATURE
A failure in the temperature sensor or circuit will result in calculated temperature being substituted for actual temperature. Calculated temperature is a predicted
fluid temperature which is calculated from a combination of inputs:
² Battery (ambient) temperature
² Engine coolant temperature
² In-gear run time since start-up
 
so check if fans are cutting in ??
Oil gets less viscous as it warms up .. I imagine this would cause slip rather than not changing up but I may be (and probably are) wrong.
If `the temp is out of range I would imagine you would get a OBD error code,although there is no mention of this in the 41TE section of the worksh*t manual .. check for error with key dance.
Also can find no mention of acceptable temp range - sorry.
Also, good to identify your vehicle as you may not have a 41TE box........