5.7 Vortec rattle sound help

[BlueZ71Hoe]

I have a 2000 Tahoe z71, old body style with the 5.7 vortec. In great shape just purchased. About 125k on it. I hear a rattle from either the engine or the tranny right when I let off the gas. Under low and moderate load there is no rattle, but it will do it a little under heavier load. Can't hear it when driving down the road only when sitting in neutral or park. Any ideas? Piston slap? Lifter? Doesn't seem like the lifter noise others have mentioned. But not sure. TIA!

 

[TigerEyz3]

Hard to pinpoint based on your description, but here are a few common "rattle" occurrences that it could be:

• heat shield (converters, starter)
  
• dust/inspection shield (between motor and transmission)
• fuel lines/filter (not likely, but possible contact with body/frame)
  
• transmission lines (not likely, but possible)

 

[BlueZ71Hoe]

Are we able to post videos on here? That may be helpful for someone to hear it. I'm wondering if rattle isn't the best description of the sound. Maybe more like a knocking or tapping.

 

[east302]

You could try a YouTube link or maybe Photobucket


Sent from my iPhone using Tapatalk

 

[BlueZ71Hoe]

You could try a YouTube link or maybe Photobucket


Sent from my iPhone using Tapatalk

Ok will do later today thanks.

 

[BlueZ71Hoe]

Ok will do later today thanks.

Here is the promised video of the sound.
<div style="position:relative;height:0;padding-bottom:75.0%"><iframe src="

" width="480" height="360" frameborder="0" style="position:absolute;width:100%;height:100%;left:0" allowfullscreen></iframe></div>

 

[PG01]

hard to really diagnose over the intrnet but that sounds more like a rod knock, maybe even piston slap, than a rattle to me but i not a mechanic...im sure someone else will know better... sorry bud

 

[TigerEyz3]

I agree with Galante...doesn't sound like a rattle, more of a "tick". Hard to determine where it's located in the video though. It could possibly be resolved with an internal engine cleaning.

• B12 Chemtool and/or Seafoam for the upper end - lifters and intake (most likely source of the noise). To clean the lifter section directly, you can remove the valve covers and shoot the chemical into the pinholes used for lifter lubrication. To clean the upper intake, you can use the vacuum line from the brake booster as your injection point (but be careful).
  
• An old-school option for cleaning the lower end is to run ATF in the oil for about 10-15min, then do an oil change service. There are lots of motor clean chemical options out there. ATF is basically motor oil with more detergents in it.

 

[BlueZ71Hoe]

I agree with Galante...doesn't sound like a rattle, more of a "tick". Hard to determine where it's located in the video though. It could possibly be resolved with an internal engine cleaning.

• B12 Chemtool and/or Seafoam for the upper end - lifters and intake (most likely source of the noise). To clean the lifter section directly, you can remove the valve covers and shoot the chemical into the pinholes used for lifter lubrication. To clean the upper intake, you can use the vacuum line from the brake booster as your injection point (but be careful).
  
• An old-school option for cleaning the lower end is to run ATF in the oil for about 10-15min, then do an oil change service. There are lots of motor clean chemical options out there. ATF is basically motor oil with more detergents in it.

Thanks for the advice. I'll try these things soon. May be a dumb question but what am I being careful about spraying into the vacuum line?

Also, I know it's hard to say, but what would I be looking at cost wise for fixing rod noise or failed lifter(s)? I do minor work myself but usually let the mechanic do bigger jobs. Thanks

 

[th3 shifty]

so i had this same thing.. just found out what it was... it was the shield on the front catalytic converter... the welds gave up and it was just sitting on top rattling away.. pulled it out... gone.. so happy