oil pressure gauge pegged past 60???
 

would a bad sending unit cause this? gauge goes back to zero when truck is shut off.

Re: oil pressure gauge pegged past 60???
 

Yes, it could be a bad sending unit. But it could also be a bad connection between the gauge & sending unit.

The electric oil pressure gauges work very similar to a gas gauge. The sending unit is zero Ohms at zero PSI and 90 Ohms at 60 PSI. Some sending units are 90 Ohms at higher pressures (when used with a corresponding higher pressure gauge).

Anyway, if the sending unit is bad or has a bad connection to the gauge (infinite Ohms), it will cause the gauge to peg beyond it's maximum reading.

To test it, unplug the wire from the sending unit and connect a temporary jumper wire from a good ground to the unplugged wire. With the key on, that should cause the gauge to read zero (or close to it) if it's just a bad sending unit. However, if it still pegs the gauge, you're likely looking at a bad connection.