whenever I hit the brakes or my truck down shifts the oil pressure gauge goes to zero for a few seconds. Not sure why this is. Is it my sending unit? I have a 97 1500

 

Check oil level. If that's good, buy a cheap mechanical gauge and install that for a few days. If your oil pressure is NOT going to zero.... replace the sender.

 

Make sure you stop by a parts store and grab the oil pressure sending unit socket and universal joint to make it easier on you. If it is the sender... Mine was easy to identify as mine was leaking oil badly. I have a post on it from a couple weeks ago with pics. Good luck.

 

Mine did that when I stopped at traffic lights. I replaced the sender, it hasn't happened since.

 

I can tell you that I had this happen and bad things were afoot. Thinned out oil can do this. Mine thinned because of a burnt plug wire causing misfire then overheating the engine and oil. This is something you SHOULD be noticing or getting a blinking check engine light about, though. Coolant or gas leaking into oil can have the same effect or even too thin of oil in summer heat. I'd check with the methods previously described, but be cautious. Listen for new taps, knocks, other sounds of potential bearing failure. Watch your temps as well. Check your oil, how does it look/smell? That's a great indicator of trouble. If all else fails, an oil change is cheap enough insurance compared to what could happen. I recommend Rotella T 15w-40. Plus you can see how the oil looks at the bottom of the pan.