2003 Gmc Yukon 5.3 flex fuel 4wd Transmission rebuilt/noise like a broken flex plate??

[Summajet]

I had a my L460E Transmission rebuilt at a local shop in Virginia. I did not hear the noise prior to rebuild.
With truck running in park I can hear what sounds like a broken flex plate. It is a low decibel sound.
I have listened to other videos on youtube.

When in gear the noise is same decibel as in park. When driving as you accelerate you can hear the sound/decibel increase.

I took it back to the shop which I heard good reviews/referrals on.
Owner lifted on rack and using a stethoscope said the sound is coming from scored piston?
Note prior to rebuilding I did not hear this noise. He opened the inspection plate for the flywheel cover and said the flex plate is not cracked/broken from a visual inspection.

Is there anything I should look for or do to try and pinpoint the noise myself?
I was thinking of using my boroscope and remove flywheel inspection cover and look as far top as I could.

Any advice would be greatly appreciated!!!!!

 

[Z28TWITCH]

Does it only do it cold? For one, stop doing ANYTHING yourself...you payed somebody to do a job and your suspecting they didn't...Take it to a different shop and have them look it over...Dont tell them what you think it is...just say, it's making a noise, what is it.
How many miles on the engine?

 

[SnowDrifter]

^^^

Don't **** with it. Take it back and let them figure it out. Feel free to discretely inspect stuff yourself but if you start pulling items apart it turns into a he-said-she-said.

Do you have any documentation that shows the noise wasn't there prior? Video? Service notes? Anything? That'll help you a ton.

As far as giving them info. Do just that. If you crawled under and heard that it was, for certain, coming from a given area, include that. But don't do the diagnosis. That just includes a bunch of shop politics between service writers and the techs in the back shop where info doesn't get transmitted. Sounds stupid, but trust me, about every damn shop works that way. Service writer disregards all info you gave them, asks tech to check for XYZ specific problem because it's faster to write up, tech checks what they were asked as a customer concern rather than a diagnostic and ships it. You get the car back wondering "what the ****."

Could you provide a good video / sound byte?

Scored piston just sounds like piston slap that doesn't go away tbh. And it's not something that 'just happens. It'll be either due to heavy corrosion in the cylinder liner from things like flooding or water ingestion, massive overheating such that the aluminum piston begins to melt, or a total loss of oil, which generally takes your bearings with it as well. Can be checked w/ compression / leakdown / boroscope through plug holes.

 

[SnowDrifter]

Oh and it can also be caused by dirt ingestion - like driving without an air filter.

Either way, piston scoring doesn't just happen. There's typically something directly causal, generally catastrophic unless you're a crackhead or something who goes around with the air box off

 

[Summajet]

I appreciate the insight. I had not had the time to check compression or boroscope yet. I had read about piston slap and thought I read it does not affect the longevity of the motor? I would think it would make motor fail sooner. Other than removing/rebuilding motor if it is a piston slap are there any fixes other than rebuilding motor?

I have to replace my water pump first on my 00 mountaineer sitting in my garage. I have not been driving it much since the sound started. Is it possible it could be an oil pump failing (pressure dropping?)
Wife recovering from ****** cancer last year is doing great! I'm behind on many projects and trying to get caught up...

Thanks!

 

[Summajet]

Does it only do it cold? For one, stop doing ANYTHING yourself...you payed somebody to do a job and your suspecting they didn't...Take it to a different shop and have them look it over...Dont tell them what you think it is...just say, it's making a noise, what is it.
How many miles on the engine?

Motor has 219,000 miles, When starting up cold it has a lifter noise and noise does lessen once it has warmed up some.

 

[SnowDrifter]

I appreciate the insight. I had not had the time to check compression or boroscope yet. I had read about piston slap and thought I read it does not affect the longevity of the motor? I would think it would make motor fail sooner. Other than removing/rebuilding motor if it is a piston slap are there any fixes other than rebuilding motor?

I have to replace my water pump first on my 00 mountaineer sitting in my garage. I have not been driving it much since the sound started. Is it possible it could be an oil pump failing (pressure dropping?)
Wife recovering from ****** cancer last year is doing great! I'm behind on many projects and trying to get caught up...

Thanks!

Wait when did your oil Pressure start dropping?



Tldr piston slap due to different expansion coefficients between different materials. They're sized to fit when hot, not when cold. It's more prominent in vehicles with shorter piston skirts - most things out there - as we lighten materials and reduce oscillating mass.


Yes, by technicality, piston slap might cause slightly more wear. In practice? Other stuff will fail first. I mean sure you could tear the engine down and find some cast iron pistons, then upgrade to a heavy duty rod and crank plus drop the redline to 4k and you won't have any slap. You'll have higher bearing wear and less power but it'll run silent if the noise is truly a concern. That being said I really don't see the benefit of doing so in an engine that is well known for running past 300k.


Now, if your piston slap doesn't go away when warm, then you have an issue! The piston doesn't take long to warm up, no more than 2 minutes. It's in direct contact with combustion heat.

 

[Summajet]

Morning, I was able to finally get it looked by a mechanic. With the motor running the noise is not coming from the Transmission. Mechanic said it is a lifter on the passenger side of the motor making the noise.
Said it could be a broken valve spring, lifter, or push rod. Removing the valve covers and running motor is only way to diagnose the issue. He said if valve spring is broken or worn I should be able to spot that right away and also by hand trying to shake the valve spring and lifter will show if it is bad or worn. If I have to replace the lifter, he said I might as well replace all 16 lifters.

Repair will require me to remove the intake and assembly to access the lifters under the intake assembly.
Shop time is about 3.5 hours for removal/install of the intake.

Has anyone replaced their own lifters and have pictures and/or a write up here on the forum? How long did it take to do it?

I was thinking of going to my local junk yard and remove/install the intake and lifters as a learning how to.

Going to access the bad parts, lifters, push rods, and valve springs.
If a lifter is bad I might as well replace all 16 lifters. Also replace the push rods while it is torn apart?

I greatly appreciate any insight, tips, and pictures on how to do the repair myself and save money.

Two months ago I replaced the valve covers. Should I replace them again as I will have torn it apart?

Many thanks!