speedo problem

My 1998 dodge grand carvan AWD van has a geeked out speedo. I'm driving and it reads ok then I slow down and it drops to zero then suddenly shoots up to 120mph. Yet im not changing speed. I got a service engine light. So I cycle my key 3x and get code 12, 45, 55. Not sure what that means so I drive to Autozone. They tell me it's a trans problem P0700 and that's it. Now what do I do? It's my only running vehicle and I'm single on fixed income SS, with 4 kids and 2 are disabled. I'm despirate to get this fixed. What do I do?

My 1998 dodge grand carvan AWD van has a geeked out speedo. I'm driving and it reads ok then I slow down and it drops to zero then suddenly shoots up to 120mph. Yet im not changing speed. I got a service engine light. So I cycle my key 3x and get code 12, 45, 55. Not sure what that means so I drive to Autozone. They tell me it's a trans problem P0700 and that's it. Now what do I do? It's my only running vehicle and I'm single on fixed income SS, with 4 kids and 2 are disabled. I'm despirate to get this fixed. What do I do?

Check the wiriung connector on the input and output sensors, the output sensor may also be defective. Here is a link to show where these sensors are on the transmission:

http://dodgedynasty.50megs.com/a604/basic.html

The output speed sensor is the signal source for the speedo indication. However, it's signal is also used for shift sequencing. Generally, if the output sensor is faulty you will see both speedo and shifting problems. That said, even if you're not seeing shift problems it's well worth at least inspecting the wire harness for chaffing and the connection for security and corrosion.

A P0700 code is a flag telling you something is wrong in the transmission and/or its electronic controls. It is non specific because the onboard fault detect system (OBDII) isn't designed to detect the multitude of faults a transmission can produce. That's where the Transmission Control Module (TCM) steps in. It will store its own set of fault codes entirely separate from the OBD codes. To read them you have to connect a scanner specifically designed to read transmission fault codes. Any transmission shop and many full service shops should be able to do that for you. If there is a code it will give you a better idea of what it will take to fix your problem. Normally they would charge around $100. I have a hunch though if you let them in on your circumstances they may cut you a break. What the hey. It's Christmas.

Not a whole lot of faith here but you could try disconnecting the negative battery cable for 10 minutes. This will rest the code and the electronics. It may just need a kick like that.