1986 camaro iroc-z28 gauge issue

im having a issue with all the gauges on the multicluster none of them work properly. example

speedometer -doesnt read at all.-
fuel gauge -key on needle moves way past F till it cant move any futher-
oil pressure -doesnt read-
rpms -key off goes to 30-35 an stays. key on drops to 0 engine start jumps to 70 till it cant move any further-

could this be a ground wire being corroded or sumthing else? ive took it all apart an i see no corroded/broken gears in any of them