I have a 2005 2500HD and have a mild knock and low oil pressure when the motor warms up... it doesn't sound like any catastrophic knock I've heard, it's more like a rattling sound. I'm no stranger to rebuilding the older Chevy motors but have never had an lsx motor apart.

I plan on having the machine shop check the bores, crank and installing my cam bearings.
I'll be buying new rings, main/rod/cam bearings, oil pump, head bolts, timing assembly, lifters, gaskets, flexplate and probably every sensor that is hard to get to.

Is there anything inside these motors that the older motors don't have that I should rather look at or just go ahead and replace?

This is a work truck and I don't want anything more than a stock rebuild.

 

Possible it is piston slap not knock. Look it up online. May be best to leave it.

 

I know what piston slap sounds like... generally you hear it more on cold starts which is not my case. Plus my lack of oil pressure.
I am not asking to diagnose the issue, I want to make sure their are no stupid o-rings or common worn hard parts inside these motors that the old small blocks didn't have.

 

How many miles are on the motor right now? I'm also assuming you're buying a factory replacement oil pump, correct?

 

Motor has around 140k I believe. I have descent oil pressure and no present noise until it warms up at which point the oil pressure drops to roughly 10 psi and makes a metallic sounding rattle/tap and it honestly sounds like it's coming from inside the bellhousing/torque converter but I suppose it could be one of the rear cam bearings, rear rod bearings or rear main bearings. I really only hear it at idle in gear on the brake (which is when the oil pressure would be at the lowest).
I've never heard anything like it before - it doesn't sound like a spun bearing or lifter tap.

And yes, I planned on buying a stock replacement (standard volume) pump. Can I save a few bucks and buy the summit brand standard volume pump? Or are these pans big enough to run a high volume GM Performance pump?

 

I've heard of the oil pressure relief valves hanging open on LS motors.

 

You are talking about the bypass in the oil filter housing?
I read the o-ring on the oil pump pickup? is an issue too.

We'll I don't have any noticeable shavings in the oil yet so if it's a simple fix it's obviously desired.

 

No, I'm talking about the one on the oil pump.

www.youtube.com/watch?v=DoCQEdXYTGQ

• Similar

 

Description sounds like rod bearings.

AFAIK no harder to replace than any older model motor. Best to do it sooner than later, in case the crank is still runnable even if maybe not "ideal".

May have been one of those "cascade" effects; starting out with the oil pump pickup O-ring, progressing through oil starvation and aeration, to bearing failure. Seems to be a fairly common failure mode.

I'd suggest the Melling 10296 pump... HV, HP, but only slightly more of each than stock (10295). Was worth around 10 psi at cruise and around 20 at idle in my LM7, using the stock 5W-30 Mobil1.

 

I haven't really ran the truck since it started. Its been sitting for a few months and I just started it to take a video.
It really sounds similar to a rod knock to me but above idle the sound goes away. I've only ever heard sounds get worse as rpms increase with internal failure unlike this.
I don't see anything abnormal in the oil so I am hoping it didn't ruin the crank or a rod cap... I guess I'll know for sure when I get it apart.

 

Well I decided to start taking out the drive train today. I had a few other issues I had to address... drive train vibration, slipping reverse, leaking power steering pump. I have everything about 50% done (pulling it all in one shot minus acessories and intake and transfer case). Found my vibration; a u-joint that was missing all of the "roller bearings" and was about 75% of the diameter.

Hopefully I can work on it tomorrow and have it all out.

 

Well that sound was a flex plate that was broken around the crank flange and cracked in 6 spots. It freely spun from the crank, I don't know how it engaged the converter!

I should have really checked the oil pressure with a mechanical gauge but since it is out already, it's still being rebuilt.