Savana2500, '00, Speedometer & gears shifting going crazy

[Pvatblé]

Hi,

Having a problem with my Savana 2500 year 2000, V6, 4.3L
Speedometer is showing twice sometime 3 time the speed I'm driving.
Gears are shifting from 1st to D over very short distance.
Sometime ABS light comes ON.
Did replace the VSS, nothing changed a thing.
Transmission is NOT slipping, I can drive around with no problem by shifting gears manually.
Where to look for next, the cluster, the ECU?

Thank for you help.