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5.3 Knocking--Update, found the problem

pvfjr

pvfjr

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So, I just bought a '04 Silverado from an insurance auction that was rolled. It's got 120k on it, and seems like a solid ride. It drives nice, aside from all the dents and broken glass. I was down with all the body damage, but this thing seems to have engine issues that they chose not to disclose. :rolleyes:

I've read up on it, but I keep finding references to people saying that "all the 5.3's suffer from piston slap, it's normal."

I don't think this is piston slap though. It's not limited to cold starts, and it does it consistently all the time. I probed around with a $3 stethoscope a bit, and it doesn't seem to be coming from the top end. I hear it a lot around the bottom of the block. I'm guessing it's rod knock. :doah:What do you guys think? There's a yard with a

Here's a little video so you don't have to listen a lot of description.

http://www.youtube.com/watch?v=kHvavctCCdI&feature=youtu.be

[youtube]http://www.youtube.com/watch?v=kHvavctCCdI&feature=youtu.be[/youtube]
 
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i would post up over on ls1tech.com tons of info there also .

that does sound BAD .

mabye unbolt the torqe convt and fire it up by its self and recheck .
 
Yeah, thanks. That's kinda what I thought. It's a shame that a search for knocking 5.3's yields nothing but people talking about a little piston slap. I may have to make a user ID over on ls1tech. Thanks for the tip.
 
Does it go away after it warms up or do it keep knocking no matter how long it runs? Had a buddy that would start up his 04 silverado and it would sound like a cummins. It would go away once the truck got warm. After dealing with it for at least a year and a half, maybe 2 years, he finally decided to start doing some investigating. He dropped the oil pan to take a look and found that his oil pickup was submerged in a thick oil sludge. Cleaned it all up and hasnt had a problem since. The oil in his truck has been changed at 3000 miles religously since he bought it with 60,000k on the ticker. My 99 silverado just started doing a similar type noise (much quieter) for about 45 seconds after startup then goes away. Also doesnt do it every time I start it.
 
free site and great guys .

i seen a big of a ls truck pan off and there is baffles molded in the floor of the pan that can hold lots of junk or sludge.
 
It's a very consistent knock, and does not go away at all when it warms up. Maybe I'll pull the pan to investigate, but I think I'd have to pull the diff first.
 
Hmm, yeah it may be easier to start investigating somewhere else first. That sounds pretty loud. Like mentioned earlier maybe check the flywheel :dunno: and start asking questions on LS1 tech.
 
How hard is it to unbolt the flexplate? Is there pretty easy inspection cover access somewhere? And if I did unbolt it, wouldn't the flexplate and flywheel just rub against one another?

What are the odds that any of this would be related to the rollover? It looks like a low-speed rollover to me, so I'm inclined to believe that it was probably knocking when it rolled.
 
convt from flex plate not from crank .

and yes easy to get to pull starter and you can hit 3 bolts to convt and hole in bottom to roll over flex plate to get all 3 .

metric bolts on these fyi and allen drive if you got it for convt bolts. tho thay do have small hex head but better bite in allen drive.
 
I just bought a '99 Silverado from a coworker. It has some sort of a knock also (not piston slap) and has had the same knock since he bought it a couple years ago. It's not the flywheel either, it looked good when we had the tranny out once. I was wondering if it might be a wrist pin or broken ring or something.
 
sweetk30 said:
convt from flex plate not from crank .

and yes easy to get to pull starter and you can hit 3 bolts to convt and hole in bottom to roll over flex plate to get all 3 .

metric bolts on these fyi and allen drive if you got it for convt bolts. tho thay do have small hex head but better bite in allen drive.
Click to expand...
Ah, well wouldn't the torque converter and flexplate rub if I unbolted them? Or would the torque converter sink back into the tranny just enough to create some clearance?
 
I had something similar several months back, had the oil pan off twice until I looked harder and noticed a scraped up cam lobe. Turned out to be a worn out lifter wheel and chewed up cam lobe.

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I'm trying to find my video I loaded up, can't find the thread I started right off.
 
my 4.8 had a similar noise, turned out to be the torque converter bolts.

had to drop the starter to tighten them up.
 
Hmm, well I'll keep my fingers crossed that it's something like those problems. I really hope it's not in the bottom end...:eek1:

Thanks for the ideas and the video. Sounds a little different, but definitely sounds like what I would assume to be too "heavy" of a sound for the valve train. Maybe that means that me disregarding my valve train as a problem was premature...? :confused:

Man, would it be sweet if it was just the stupid torque converter bolts. :woot:
 
Yes, check the easier stuff first, that's what I was doing, then finally had to tear into it further as things went.

I had several people tell me that it "shouldn't" be the bottom end, that's supposedly one of the major improvements GM made to these engines, making them "priority mains" oil pressure/pump supply.

I even went so far as to replace the oil pump on this thing first.

it wasn't a very inexpensive repair either, not like my old '89 TBI engine anyways, about twice as much and I didn't even do as much as I did with the TBI engine.
 
pvfjr said:
Ah, well wouldn't the torque converter and flexplate rub if I unbolted them? Or would the torque converter sink back into the tranny just enough to create some clearance?
Click to expand...
Nevermind, answered my own question by reading 4xcrazy's entire 10-page post. I guess I can just shove the TC back a little bit after unbolting them.
 
pvfjr said:
How hard is it to unbolt the flexplate? Is there pretty easy inspection cover access somewhere? And if I did unbolt it, wouldn't the flexplate and flywheel just rub against one another?
Click to expand...
The inspection cover on 4L60E went away and now it is a solid bellhousing. There is a little 2" or 3" hole you can uncover to look up there. You will need to remove the starter to get to the the converter bolts. I find that you can disconnect the battery and leave all the connections on the starter in place. Just push it back or hang it from a coat hanger or something. This will save a lot of time since you need to remove and replace the starter twice for this experiment (and you never know when you will break off the little terminals). You can get a prybar in the little hole and turn the engine by the flexplate there.

As you already found, the converter can push back a little into the transmission pump once it's unbolted.

For any noise that could be lube related, make sure there is a decent oil filter in place and not a FRAM. (For Ruining A Motor?)
 
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