2000 cirrus code p0720

Hello
i have 2000 chrysler cirrus lxi,v-6.auto od trans
after driving car 1 hour or more, spedo starts to jump around
and sometimes goes to zero,then when coming to a stop,jerks hard.check engine light comes on, then will not shift, turn off and will be ok until
spedo goes crazy again,replaced both speed sensoes twice and still
same problem, until spedo acts up trans shifts perfect.
any ideas ?????? wirring ????? trans module ?????
any help would be appreciated !!
thanks