Just got the truck on the road, and the speedometer starts jumping around and mainly stays between 50-70 mph, no matter how fast your going. I installed a new speed sensor but to no avail. Is there anyway to take one of the wires from the sensor and ground it to by-pass the rest of the system. Might tell me if its a ground problem or if its something else.

I had the adapter box between the sensor and the trans apart and cleaned it all up, but it still jumps around. The gear inside looked ok, teeth still there. Any ideas on where to start?

 

clean all the connectors if you havent already, and check the grounds on teh engine block. The main one from the battery and the alt ground( located front of block under thermostat housing)..
Check your dash panel ground as well.
if that doesnt solve the problem , insepc the drive shafts for the VSS and the gear reducer( between VSS and tranny) they can get rounded off..
then I would go to the drive gear in the tranny itself and see what kind of shape thats in..

hope this helps...

 

Oh, is th odomenter still working correctly? that wil lindicate if you have a problem in the entire system of jus tin teh speedo.....

 

No, the odometer is NOT working correctly. TOwn is like 5 miles away, and round trip in yesterday was 18 miles....

IT wants to work, just bouncing and not reading it right.

 

sounds mostly like a bad ground or loose wire in teh harness somewhere that is sending an intermitant signal, except for the odometer. tha twould lead me to check the drive shafts of the VSS, rigth angle gear reducer and drive gear. sounds like one of them is freewheelin'

 

I got it fixed. I spliced into the ground wire to the speed sensor and grounded it to the cab, it now works as it should. Thanks for the help guys.