tracked down an oil leak.

[Hillbillybuddha]

But what is this thing that the leak is coming from? It's right above and back of the oil filter. Has a couple of wires sticking out of it. I think it might be, but I'm not sure if it actually is, an oil pressure sending unit.

 

[datzenmike]

Yup most 4x4 have it. They are about $18 at Rockauto/NAPA. You can remove anyway you like, but lightly hand tighten and then slip a 1/2" or 5/16 wrench (I don't think it's a metric fitting) in behind and tighten with that. Twisting it on tightly by hand is not good for them. (and I know)

 

While at NAPA get a proper NAPA gold filter for your truck. Fram have fallen a long way since your dad used to use them. One of the poorest quality filters out there today.

[Telkwa]

I think the location is the same for all the trucks, but apparently there are a few different kinds of sending units.  Perhaps your truck has an oil psi gauge as well as an idiot light?  Our 2WD truck sending unit has just one wire.  It was leaking badly for years.  I thought I had a rear engine seal going out.  Now I'm hoping it was just the sending unit.