98 Passport 3.2 speedo quit and tach flutters

[bdw_sre]

Can anyone HELP point me in the right direction as to what is causing tach to flutter ( idling- tach reads 2500 to 3500 steady), no big change when you rev the engine. Engine runs fine on the highway, no misfires or surges. Speedometer was working fine, but now it has stopped working. Engine temp gauge has started to show hot, but temp is normal. I checked all fuses and relays, all seemed ok. Cleaned battery terminals and left battery disconnected for 20-30 mins. Restarted engine and same thing. Any suggestion?????????