TPS? Speedo gears?

[Fluffrider]

1992 3/4 ton auto. 500 miles from 300000

My speedometer bounces all over the place and my overdrive has problems engaging and once it does it does not like to stay in OD. Are these two problems related? Does anyone know how to fix this ? Thanks

 

[cerberusiam]

Yep, the VSS signal is probably the source of the problem. Likely the drive portion of the VSS is worn or loose, or, you have a connection issues. Start at the trans and work back thru the harness checking things.