2nd Gen Non-Engine/Transmission speedo flying away...

[98rammer]

it's happened before, but in the past week it happened about 3 times. i'll just start rolling and boom my speedo runs to about 50mph and falls back down to 0 (or however slow i'm going). anyone had this? being a 12v, it's all mechanical right? is the guage itself mechanical or electrical?



Tom

 

[braible]

check this

sorry to say that it is electrical. from the transfer case, to the PCM,to the speedo.

you might check the connections, to see if they are loose or dirty.

 

[vssman]

Tom,



Yup - it's electrical. The mechanical end of it stops at the sensor. I had a similar problem (reading 30 MPH at a light) and cleaning the TPS helped.

 

[raychem]

wako speedo

I had the same problem recently. I went ahead and replaced the vehicle speed sensor that is located in the tailshaft section of the transmission. If your truck is a 12v this should solve your problem.

 

[jrollins]

i second that , it sounds exactly like a rear wheel speed sensor failure, the sensor is mounted on top of the rear differential if u have a 24v and bolted in. its a pain to remove sometimes, just warning u!.

 

[vssman]

Tom,



Your VSS sensor is located on the side of the transmission. 24V trucks use the ring gear on the rear end. 12v vss sensor usually don't go bad. It's just a rotating magnet and a hall effect switch. I'll look and see if I have any laying around but I think I tossed all of them when I clean out my desk at work.



Edit: Tom, I've been told that your truck may not have a vss sensor in it and may actually operate like the 24v trucks. I know they changed the system during model year 98 but am not sure exactly when.