2003 Ranger Speed o meter bouncing

[sriley1358]

At idle, my 2003 ranger with the automatic transmission and 4.0 liter engine (4x4) has a bouncing speed o meter. If you rev the engine it falls back to zero. It works fine going down the road. Just at idle it bounces up and down between 0 and 20mph. Is this a result of a failing OSS?

 

[Yellowsplash]

Clean off the pickup on the abs sensor in the rear diff...