I have a 1993 town and country front wheel drive v6. every now and then the transmission drops into low gear and refuses to shift. Manually shifting the transmission doesn't effect it. the speed sensor has been replaced. IF the vehicle is shut off for a minute, it will then run nornally again.. Any ideas? thanks.

Optional Information:
1993 Chrysler town and countr 3,3 liter v6

Already Tried:
the transmission has been looked at by a trans shop, which replaced the speed sensor module. Still happens, doesn't seem to be temp, or speed related./p>