speedo is going crazy

[94GTMOOSE]

My speedo works 70% of the time while driving. It will be working fine for most of my 30 min commute then the needle will start bouncing up and down. and then it just stops in one spot. I did notice that both the odometer and tripometer do not work when the speedo freezes in one spot. It has never started working again while driving, it always just resets itself by the next time i get in the car.

I am not sure how the speedos in our cars work so i dont know where to begin diagnosing the problem.

I would take a video on my iphone and post it, but i am concerned with the safety issue doing that while driving.

 

[Chythar]

Sounds like to me that your VSS (vehicle speed sensor) is dying or there's a wiring problem. Have you changed the gear on the VSS, for 3.73 or 4.10 gears? If you have the white 23-tooth gear, it could have stripped.

 

[94GTMOOSE]

Not sure what color gear is in there. I did have the trans swapped from auto to t-5 about two years ago. Is a VSS a easy part to change?

 

[Chythar]

It's a blue sensor sticking out of the transmission near the back, I believe it's on the driver's side. One bolt and it slides right out. Have you (or a former owner) upgraded the gears in the rear end?

 

[94GTMOOSE]

The gears are 100% stock. That is my next project. I'll just buy both the speedo gear and VSS. Can't be more then 50 bucks for both.