Main bearing knock

Randyd · April 14, 2016

I have an 2005 Chevrolet Silverado 1500 extended cab Z71 with the vinB 5.3 L33 with 216000. Its got what sounds like the rear main knocking. I've only owned the truck a short time. Body and interior are in excellent condition. I bought it cheap enough knowing that it might not last long. That being said I'm wondering what all other engines will be plug and play for this truck? I would like to go back with the L33 but it seems that they are more pricy than some of the other 4.8 or 5.3. Any advice would be appreciated thanks

O_J_Simpson · April 14, 2016

They all knock. Just keep driving.

Randyd · April 14, 2016

I plan on driving it until it dies just wanted to have a spare in the garage ready to go. The knock is coming from the oil pan and it's loudest where the transmission bolts on. Will a thicker oil help quiet it down any?

newdude · April 14, 2016

I plan on driving it until it dies just wanted to have a spare in the garage ready to go. The knock is coming from the oil pan and it's loudest where the transmission bolts on. Will a thicker oil help quiet it down any?

I'd be pulling any sort of inspection cover on the transmission and looking for a cracked flywheel. They can sound exactly like a bad lower end knock, and Vortecs are known for them, especially 4.8 and 6.0. Seeing you said the noise is loudest there, I'd check that first.

Randyd · April 14, 2016

A little more information. The noise while driving gets significantly quieter while driving as it warms up but stays the same at idle. Also the oil pressure is very weird. At cold start up it hits 40 psi and stays there idling or driving. After it gets about half way to operating temperature it goes to 20 idling and 40 driving then when it gets completely warmed up idles at 40 and runs 50+ driving. I've never seen an engine oil pressure change like this. Anyone else ever seen this?

C/K Man · April 14, 2016

For sure on the flywheel, but that sound shouldn't change when the engine warms up. As for the oil pressure, these trucks have so many problems with the gauges the only way to tell for sure is with a mechanical gauge. It's normal for oil pressure to be higher when cold, when warm you only need about 10 psi/1000 rpm. If you are not hearing lifters good chance it's O.K..

Randyd · April 14, 2016

I am definitely going to check flywheel but that was my thoughts also. I thought the same as you on the oil pressure but this seems to be just the opposite as normal. That's what makes me wonder wth is going on.