Need help. Weird electrical problems. Some gauges occasionally malfunction (fuel showing empty on a full tank, volt or battery gauge pegging at 19 volts, RPM gauge dropping to zero when driving. Transmission (only 15,000 miles with new rebuilt) starts slipping occasionally when up around 60 mph after running for just a little while. Transmission runs with no issues under 50. Is there some kind of engine control module that could be malfunctioning and affecting everything? I've checked battery and alternator and are working fine, according to Auto Zone.