Just until today my 2000 Neon has never done this. The needle to the speedometer jumpts from 0 all the way to 120 and when it does it feels like if the governor or speed limiter is kicking in. I drove about 22 miles from work and the needle didn't even move and the last 3 miles the needle jerked around a little bit and then the limiter would start to kick in. Is this the VSS sensor. I know it's not my cluster because when the speedometer is at 0 the lockup isn't engaging in my last gear but as soon as it does work for a couple of seconds the convertor will lock up in third gear. I was thinking that It would be the VSS sensor or the TPS sensor, but like some of you might say the TPS sensor doens't send a voltage signal in reference to the speedo. I did test out the guages to see if they work. You hold the trip/reset button and cycle the key off and on about 5 times and your guages will reset themselves.Any help is greatly appreciated.
Thanks,

 

if there is a way to check the pcm, i would do that.

 

I have just gone through something similar. I changed both input and output speed sensors. Apparently they are a notorious part and let go often. I havent installed them yet because I havent had the time and I already put mine away for the winter but i can almost guarantee its them. The shop my friend works at said they used to but them by the case because the caravans and others use the same sensor and they all go bad.