Speedo problem

[Cratos]

I have been having a problem with the speedometer acting up. (Jumping around a bit) so far I have replaced the Speedo, sensor and pigtail for the sensor I can not find any bad wires. I pulled the rear cover and cleaned and inspected tone ring all looks good no missing teeth. So I am still at odds needle still quivering and @ 80 goes nuts.
So I am stumped! Where is the abs box and can I unplug it and see if it could be causing the problem? What else it there??
If I try and use the cruse it is not happy you can feel it trying to comp for the Speedo.

[JSchuricht]

Could be the PSOM. Check the junk yards for a OBS 150-350 or bronco, pull the speedometer from the cluster and swap it.

[Cratos]

i already have one doing the same thing. at same speeds

[eaglefire]

had the same problem,tried the same fixes. then trashed the l/s when i had machine shop do the bearings the tone/abs ring was bent mystically somehow. anyway according to the ford mechanic the ring is a soft metal that can warp from heat (heavy towing, offroading) new ring and havent had the speedo jump or cruise surge sense.

[Cratos]

Hate to ask what that cost. but what did it cost?

[eaglefire]

50.00 from ford for the ring , r& r the third member. unless you need to replace ring & pinion or bearings you would just be replacing tone/abs ring . keep your shims the way they come out, dont bang the bearings. the ring is r&r with a hair dryer,(you dont need to use high) that is how sensitive it is . i wont tell why i had to barrow a hair dryer to do mine