1992 Dodge Caravan Speedometer/odometer don't always work

I have been having some trouble with my Caravan's Speedometer and odometer. Sometimes they will work right off the bat and be fine, other times they won't work in the start of the trip the the needle wavers and they start working. Then sometimes it'll be going fine, the needle will waver then go to zero. Whats wrong and what can I do to fix it?

CHeck your input and output sensors on the transmission. Look on the driver side engine compartment, follow the transmission cooler lines from the radiator to the trans, you will see them on either side of the lines on the tranny.

Look at this site it shows them a turbine speed sensor (input sensor) and output speed sensor:

http://www.robskorner.org/faqs/Trans/a604trans33.html#93v