2007 GMC Sierra 3500
 

I just bought a one ton duelly with a flat bed. It has the 6 litre motor. At 351 miles we had to have it towed because of low-no oil pressure. I went yesterday to pick it up with its new oil pump. The oil pressure only got up to 40 psi when it downshifted for the hills. It seems to me that a new engine would have close to 40psi at an idle. My brother has the next size down v-8 and that is the case with his. Let me know what you think. Thanks