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TrailblazerSS
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Discussion Starter #1
I just got a 2007 AWD that has a "knock" and have been doing a bunch of reading on the site. Thanks to all the members for the wealth of information so far.

My LS2 has what sounds like a rod knock but it's so quiet that it has us perplexed. I know the motors make some noises but here are my observations so far:

- Doesn't knock when it's on high idle on a cold start. Only when it drops down to a normal idle
- If you put it in gear and load up the converter to 2k, it's a little louder. I haven't driven it at all
- At 2k RPM in neutral, the knock disappears :dunno:
- Two front exhaust manifold bolts are broken off. One Driver Side and one Passenger side. I don't see any "black" that indicates an exhaust leak and the sound is the same from each inner fender well so it seems to me that it's in the motor somewhere.
- Oil presssure is 40 PSI + on the factory gauge (inaccurate I know)
- No codes are triggering
- I took an oil sample to send to Blackstone Labs today
- No visible metal in the oil filter (I have a oil-filter cutter)

It has 76k miles on it and I'm planning to pull it on Thursday/Friday this week. I have the PCM of NC pickup mod ready to install and plan on resealing the diff since it's leaking at the pinion seal. Just wondering what else I should plan on doing while it's out, and what I should be looking for.
 

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TrailblazerSS
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Discussion Starter #2
The task list while it's out so far is:
-Determine the issue
-New seals and water-pump
-Replace Lifters
-New starter
-XS Power Headers / Catted Y
-Get broken manifold bolts out
-Replace Power Steering lines due to rust while motor is out
-New oil pickup tube/baffle install
-New fuel lines since they are rusty near back of the trans
-Reseal the diff
 

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06 3SS TBSS RWD
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A lot carries on condition of the motor. If the motor is knocking, then time for a forged bottom end. I mean while its out and your budget allows it, forge the bottom end, ported/polished heads, cam package, a stall and go from there. A lot carries on how good/bad your bottom end is. If you catch it now, the price won't be TOOOOO bad as you can send your bottom end off as a core.
 

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Discussion Starter #4
I know everyone jumps to the inevitable conclusion since spinning bearings is common but it really doesn't sound that bad yet. I'm not going the forged route until I see the crank but I know it's a possibility. Would be nice to hone it for forged pistons and drop in a balanced rotating assembly.
 

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But if that metal you see is coming from the bearings, youd be wise to pull it and fix it now . It will be cheaper than waiting until it blows a rod out the side of the block. Then you are stuck with a $6000 bottom end that you could have paid 3500 for.
 

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Discussion Starter #6
But if that metal you see is coming from the bearings, youd be wise to pull it and fix it now . It will be cheaper than waiting until it blows a rod out the side of the block. Then you are stuck with a $6000 bottom end that you could have paid 3500 for.
I agree with that. Plan is to take it out on Thursday since it's already on the lift but I was wondering what else I should budget for while it's in shambles.
 

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If the block is good , then i would replace water pump, oil pump with a melling high pressure, do the pcm pick up tube or c6 pan, headers, plug, wires w ith heat socks, maybe the starter while youre at it. You can clean up the wireing too since you have the motor out. Replace all the header bolts with either studs or upgraded bolts. If you can budget it, thro a cam setup in there and a stall. All easy work with the motor out.
 

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Discussion Starter #9
Found the issue today. #1 slug got beaten by the ugly stick. Probably piston slap degrading over time is my assumption.

Guess I'm rebalancing the assembly with forged pistons, doing a melling high pressure, all new valvetrain and freshening up.

Also found three pushrods worn at the rocker side. I assume due to LS2 top end oiling issues that the melling pump helps with.

 

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If the block is good , then i would replace water pump, oil pump with a melling high pressure, do the pcm pick up tube or c6 pan, headers, plug, wires w ith heat socks, maybe the starter while youre at it. You can clean up the wireing too since you have the motor out. Replace all the header bolts with either studs or upgraded bolts. If you can budget it, thro a cam setup in there and a stall. All easy work with the motor out.
do this reliable more fun truck to drive!!
 
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