The oil pressure on my truck drops once it warms up and the RPMs are low. I push the gas and the problem goes away. There is also a knock that occurs when I place in gear, once I go back to park or neutral the knock goes away. I am thinking that my oil pump is going (decrease oil pressure) and the knocking is a lifter as a result of the low oil pressure. Any thoughts or ideas?

 

It could be the oil pump , more likely a clogged oil pump pick up tube screen , common problem ... Lew

 

Thanks Lew. I considered this as I read it in a few other posts but I was thinking that as the vehicle warmed up a clogged pick up screen would actual work a bit better and therefore would have poor pressure at the start. The reverse of my current situation.

 

You are thinking correctly. A clogged screen would also allow for good pressure at idle, but would lose pressure as RPM and oil flow rate demand increased.

It sounds like either the oil pump is worn, or the bearing clearances on the rods and mains have gotten too large for the oil pump to keep adequate supply.