Speedometer Woes

[rb68rr]

On the highway the other day my speedometer went nuts. I had the cruise set at 65mph and all of a sudden it started really accelerating. Glanced down and the speedometer had shot up to 100mph! Then it dropped down to around 50mph and then back up to 110mph! Then I disengaged the cruise. About 1 mile later it jumped up and down a couple of times and then quit completely. BTW, this was with temperatures in the 30's. Now that it has warmed up to the 50's it will work from a dead stop up to about 50mph with a little jumping around and then drop back to nothing. I unscrewed the cable at the joint and could spin the top part by hand and the needle would move. I then took off the cable from the transmission. I took apart the little box with the metal gears inside and they would all turn freely. Also the bottom cable would turn freely. What is making it drop back to zero when I get up to around 50mph? Oh, and I'm also getting the code 24, vss. Thanks, R.B.

 

[GNVenom]

You have a defective VSS Buffer.

http://www.installationinstructions.com/FYI/vss-tech.pdf

for some info.

 

[mikestertwo]

I took apart the little box with the metal gears inside and they would all turn freely. Also the bottom cable would turn freely. Oh, and I'm also getting the code 24, vss. Thanks, R.B.

If there is a little metal box attached to the trans that means you have a speedometer correction gearbox on the car. Did you check the gear inside the transmission? The gear could be worn, either the teeth on the gear or the square hole in the end of the gear shaft where the cable plugs into could be rounded. You could also have a gear slipping on a shaft inside the correction gearbox. Remove the gearbox and plug the cable directly into the trans. The speed will probably read off a bit without the gearbox. If the problem goes away the problem is in the gearbox. If you still have the problem take a look at the gear in the trans. You will get a code 24 if the speedometer stops working because the speed sensor for the computer works off of the speedometer rotating magnet.

 

[rb68rr]

Thanks. No I didn't check the gear inside of transmission. I will try it without the gearbox tomorrow and see what happens. Thanks again. R.B.