when i bought my car the speedometer, temp. gauge, tachometer, oil service lights and inspection lights didn't work. I replaced the batteries in the SI board and now everything works except the speedometer and tachometer. (however the oil service and inspection lights come on at random so if there is anyway to disconnect them it would be desired at least for me)
I have also checked the speed sensor in the differential and didn't see anything wrong with it, so if anybody has anything else about the speedometer repair that would be nice.