Knocking/ Chattering at high rpms

[19964x4HOE]

hello,

Id first like to start off with saying i am new here and this is my first thread. BUt i have been a member on other auto forums so this isnt my first time on a forum. I jsut purchased a 1996 Chevy Tahoe about 3 weeks ago. It is 4WD, 2 door bone stock. And i just noticed that there is a slightly loud knocking/chattering noise coming form the engine bay only at 4k rpms and above it seems like. I have seafomed the engine and tried some oil treatment stuff and that didnt do anything. Anyone have any ideas? Thank you very much

Bryant

---------- Post added at 04:14 PM ---------- Previous post was at 04:09 PM ----------

btw its the 5.7 with 4L60 tranny

 

[Gzes]

When I got my truck out of my back yard and decided to fix it up I had a problem. It worked and ran good but the oil pressure was always low. I would rev it up and the pressure would go up. So I didn't use I as a daily driver but then it started to know very little and I had to get the complete overhaul because the crankshaft was extremely worn. Migh be your problem also. By the way it's a 2 door hoe also look at my avatar. It only cost me $1400 to fix so...

 

[SunlitComet]

hello,

Id first like to start off with saying i am new here and this is my first thread. BUt i have been a member on other auto forums so this isnt my first time on a forum. I jsut purchased a 1996 Chevy Tahoe about 3 weeks ago. It is 4WD, 2 door bone stock. And i just noticed that there is a slightly loud knocking/chattering noise coming form the engine bay only at 4k rpms and above it seems like. I have seafomed the engine and tried some oil treatment stuff and that didnt do anything. Anyone have any ideas? Thank you very much

Bryant

---------- Post added at 04:14 PM ---------- Previous post was at 04:09 PM ----------

btw its the 5.7 with 4L60 tranny

If you can get a video or audio file posted of it It will help aot to diagnose it.

 

[retorq]

I can count the number of times in a typical week that my truck sees 4K or above ...

 

[19964x4HOE]

ok i will try to get a video of it here in just a little bit...

And i dont believe my truck sat for awhile before i got it. I have checked all the obvious things already. The truck is holding perfect oil psi. Its not throwing any codes other than a code for each Pre-Cat o2 sensor... but i doubt thats making it knock..

---------- Post added at 06:56 PM ---------- Previous post was at 06:53 PM ----------

im not saying i floor it everywhere just this was the first time i actually floored it bcuz my buddy in his 94 Full size blazer wanted to race lmao. And now since i heard the sound its always bugging me..

 

[19964x4HOE]

ok here are a couple videos you cna kinda hear it in the top end. Listen closely...

http://s1137.photobucket.com/albums...tion=view&current=2011-08-21_21-53-52_367.mp4

http://s1137.photobucket.com/albums...tion=view&current=2011-08-21_20-30-06_464.mp4

 

[SunlitComet]

The noise seems to be tied the the vibration high point of engine. Seriously that sounds like a loose or broken heat shield on the catalytic converters or other piece of metal flapping around down there like shields on exhaust manifold. Not surprising giving the exhaust one of your truck. The fact that it shows and quickly disappears in a specific range means something is buzzing around.

 

[19964x4HOE]

ive shoke and pounded on all components of the exhaust. Nothing is rattling from what i can find

 

[SunlitComet]

lower bell housing inspection cover on tranny? protective drive-train shields. maybe even broken substrate in the cat converters?

 

[19964x4HOE]

nothing is shaking in the cats. And no covers or shields are vibrating....