95 GMC 5.7 L oil pump buzzing sound.

have you isolated the buzzing sound to the oil pump? what is the oil pressure reading on a psi guage? possibly could be the pump used in the crate motor...I assume from your post, other than the buzzing sound everything else about the motor running, is fine and sounds "normal"...have you driven it at all....does the "buzzing" sound get louder when you bring up the rpm's slowly?

At idle, 40 psi. At 2000 rpm between 40 and 80 psi on dash guage. Ran fine when test drove. Put stethoscope to oil pan sump, and buzzing is clear as a bell. Trans not making any noise. Quiets up when rpm is brought up.

sounds to me that it is indeed in the oil pump. in my opinion, next step would be to change out the oil pump...and i know that's a lousy option...

Yup, especially being 4WD. Oldcapenter, thank you for your feedback.

I'm going to call the manufacturer of the engine.... Hopefully something good comes of this.

Your Welcome, and I hope there is some type of good remedy with the manufacturer

Did you ever find the problem. I'm having the same issue new crate engine installed on my 97 k1500.