KNOCK NOISE AT 2500 RPMs

[napcop]

My ride is a 2007 denali 6.2...
I've read all of the other post about piston slap, lifter noise and the like. Mine also sounds like a diesel at cold start, but that goes away when warm.

BUT WAIT... THERES MORE...

Once warm, at about 2500=3000 RPM there is a distinct metallic noise. Sounds like if you put your tongue to the roof of your mouth blow air through like a kid to make motorcycle noise. It's rhythmic, and gets faster when increasing RPMs. When under load, like going up hill, EVEN LOUDER and more distinct.

It's just out of warranty, but the dealer sounds like they're gonna take care of me. we'll see. It's going in on monday. They have to know what this is... come on now... it's a GMC dealership. can't tell me i'm the only one...

any thoughts on the 2500 RPM rattle noise? It's not the tranny... had that fixed last month. THat's what they attributed it to, but it persists. (Tranny had the hard 2-3 shift and slow=to=reverse... said it was a clutch housing/seal issue... seems to be fixed.)

 

[KMeloney]

I've got the same metallic rattle/clanging sound, exactly as you described. There are other posts here on the same subject, but I don't know that anyone has reported on a fix. I've heard that it can be anything from pre-detonation to coolant lines clanging together.

Please, whatever you do, POST BACK HERE upon getting your truck back from the dealer. I'm really interested to know what the problem and fix are.

Thanks!

 

[mattah]

I havent had this sound thank god, but i am having a high pitch sound. It gets louder when i accelerate... Does anyone have this?

 

[JennaBear]

I had the same noise at start up (especially when cold) as well as at some highway speeds. Dealer replaced all lifters, noise is gone, and she runs much better.

 

[napcop]

Back from dealer...

i've got the same metallic rattle/clanging sound, exactly as you described. There are other posts here on the same subject, but i don't know that anyone has reported on a fix. I've heard that it can be anything from pre-detonation to coolant lines clanging together.

Please, whatever you do, post back here upon getting your truck back from the dealer. I'm really interested to know what the problem and fix are.

Thanks!

well. Isn't this nice. Went for a test drive with the mechanic, i drove. His response was "that sounds like a deisel." my response was "yeah. I know." he assured me that since the same thing is also happening to a 2010 denali w/ 40k miles, it's normal. Gm backed him up with "gm corporate bulletin #01-06-01-028b: Engine knock on cold start". I'm sure the the person from the 1-800 gm customer assistance line is a great husband. He listened very well. That's where the service ended. Typical "were sorry to here that, we'll see what we can do" crap, but no delivery. I think they are scared to death that a recall would cost big bucks, and are hoping that most people aren't in tune with their vehicles and don't notice the internal motor guts rattling around until way-after that warranty expires. With the rattle i experience, i can't imagine getting another 50k miles out of this 2007 truck. Pathetic. With the total lack of customer service, this will be my last gm product. Having married into a gm family with a loyal father-in-law that gave 44 years to gm, that is a bold step for me but a necessary one.

If anyone has suggestions after reading my initial post, please respond.

Jenna, where is your dealer? Seriously.

 

[AZSCTACO]

I had the same thing a couple of years ago on my 07. Here's my story:

Had the same issue with the defective lifters and I believe that there was/is a TSB for this. Anyways....brought it in and they tore into the motor and replaced the lifters because i was getting the start up/metal noise many of you have heard.

After it was done, I was still hearing odd noises and it got faster/louder as the RPM's got higher.

So the long story short is that the defective lifters had done there damage on the cam since that what they are being pushed up and down by. They had to replace the cam and all is good now. GM better hope that all these noises you guys are hearing isn't cam issues caused by the defective lifters cause it will cost them a pretty penny. Mine was covered under the Drive-train warranty but the receipts added up to $6,000 if I had to pay.

Keep this thread updated with what you guys find.

 

[JennaBear]

My dealership (not where I got the Yukon), is in San Diego.

 

[napcop]

Brought Denali back to dealer today for regular service, and told them the noise is still there, worse when hitting bumps on the road & still constant during and after a 400 mile road trip when the motor was plenty warmed up. I took the mechanic with me for a test drive. He had me power brake in a parking lot. No noise. So he went back, and used some sort of listening tool. Found that the motor is running fine, but there is noise in the front axle/drive train/wheel bearings. Makes sense; no noise when vehicle not in motion.

She comes home for the week-end, back in next week when parts are in.
AT LEAST THEY FOUND SOMETHING!!! Any bets on the final diagnosis? More posts to follow next week....

 

[napcop]

Final diagnosis

Dealer used what they call "chassis ears" and found noise in the front differential. drained fluid and found metal particles. They are going to replace it, but my question is what caused this? any ideas are more then welcome...
~napcop

 

[napcop]

Dealer bailed on me. excuse after excuse, delay after delay, "not this week..." (again). Went to another dealer. PHENOMINAL. They truly get it. They got my truck in the same day. Covering all repairs evan though I "timed out" on the warranty. "at 86k this shouldn't happen, regardless of time." wow. So... the verdict....

--> inside of front diff casing has marks and rough spots from casting that weren't ground down. even with diff fluid only 2 weeks old, it looked like metallic paint, and had chunks of aluminum in it. JUST TO BE SURE THEY FIX WHATEVER DAMAGE WAS DONE THEY'RE REPLACING THE ENTIRE FRONT DRIVETRAIN; DIFF / BEARINGS / SEALS / SHAFTS.

I have to be honest, my opinion of GMC was quickly going south, but one honest sales team is bringing me back. THat's right SALES team. I went in looking for a new truck, and when I belly ached about my issue at the other dealer, he brought me right over to their service mgr..."you don't need a new car, you need a good service dept" THAT WAS THE SALESMAN TALKING. His payday will come. He knows I'll be back and ask for HIM when I do.

I hope this helps at least one person. I don't have the truck back yet, but I have every confidance in this Dealer. Besides, the whole front end will be new. PM's are welcome if anyone has ??'s