Mitchell_B

You had to be lucky with the C8Z. Either you had a ‘good’ one or you ended up dealing with engine or trans problems.

mfain

Thanks. Let us know how that comes out if you hear the results.. Even looking at the driver's side, I would be concerned that getting the cam cover back on with the gasket and sealer exactly right to prevent leaks might be an issue. The techs at dealerships working on the cars are neither rocket scientists nor GM engineers

OnPoint

Hopefully they've fixed this on the production line.

RapidC84B

Exactly… my order was accepted last week. Probably TPW in August.

OnPoint

Mine too. My guess is, since they've already issued a TSB, that engineering has addressed it in the PBC. I certainly hope so, anyway.

AzDave47

They did such a good job correcting the valve guide problem on the LS7, I have full confidence in them (sarcasm).

mfain

It would be interesting to track VINs on cars with the problem. What was the highest VIN (latest build) to experience the problem? That might give us an idea of whether or not the issue was addressed on the assembly line. I am skeptical. I ordered one of the last 2006 Z06s built with assurances that the previously identified roof delamination problem was fixed. After I received the car and an almost immediate recall to replace the roof, I was told that rather than changing production in mid-year, they waited until the 2007 model production run to introduce the fix. Cheaper to warranty a few cars rather than shutting down production to make changes. Then there is the LS7 that continued to have issues after GM allegedly introduced the "fix". Does anyone know for sure how the cam caps are torqued during original assembly - manually or machine? Reading the TSB they state that loosening and retorquing the caps "realigns" them, yet the procedure states "Do not remove or physically try to shift, wiggle, or adjust the cap seating". This seems to indicate that the cap torque was the issue, not necessarily alignment.

Redc8z06

Here is the TSB

z28lt1

I strongly suspect they would going forward, those are big warranty costs for them not to.

Problem is, we have no idea what the engine inventory is. Are cars built next week using engines built last week, last month, 2 months ago? We just probably will never know.

348SStb

Are any of our forum experts able to dig deeper on the issue of whether this engine issue is being/has already been corrected on the production line?

I am scheduled for production July 17 and I would be concerned if my engine were to not have the fix.

Higgs Boson

Mine was produced in January and doesn't tick or leak transmission fluid.

What percent of the cars have the tick or leak?

is that how we know corvettes are old man cars? they exhibit similar issues?

348SStb

What a useless post.

Higgs Boson

two wrongs don't make a right, 348.

adamsocb

Picking up where I left off in the production tracking thread:
I noticed the tick at about 200 miles on my car. I have been very involved on both this forum and the other one discussion the issue. I have been to the dealer to have the service manager compare my noise to the recording in the original preliminary investigation bulletin. We agreed mine sounds like the bulletin example. When I got my first oil change a couple of weeks ago the dealer's technician said he had not heard one that sounded like mine. I have listened to at least 4 other Z06s and none of them have the loud tick like mine. In addition to GM's assurance the noise creates no durability concern, I am doing periodic Blackstone oil analysis (still waiting on the first sample results) to check for any abnormal wear.

To me, the current TSB ticking repair seems more like engineers found a tweak through experimentation that reduces the loudness of the tick on most or all engines they have tried it on. This does not indicate they have found the root cause, or yet know how to correct it in manufacturing or assembly. The random nature of the problem would indicate it is probably not an assembly process issue. If the TSB procedure to loosen and retorque the cam bearing caps with the adjacent valve springs unloaded was not part of the assembly that would seem easy to implement and would only add maybe 10 minutes to assembly, although I would think that has to happen anyway to verify the valve lash shim adjustment.

The TSB was issued just over a week ago on June 28. It was only days after the engineers completed the repair on two known test cases in Ohio. This all happened pretty rapidly for GM, considering the preliminary investigation bulletin came out in early May.

I have no idea how far ahead of car assembly engines are built. If we assume engines are assembled a minimum of 2-4 weeks before vehicle assembly then engines being used next week would have been built before the first field repairs were tested. Some version of the fix may have been implemented, but we have no way of knowing.

If a correction to the engine assembly process was implemented around the same time the TSB was issued, those engines would likely be put in cars starting in late July. A good indicator will be to see if the noise stops being an issue in cars built starting in August.

The worst case scenario would be that they have found the root cause and either have not yet come up with a manufacturing/assembly fix, or the fix is too costly and/or time consuming to implement on a running basis. If it is only an assembly process change, that could happen on a running basis and certainly should occur over the July holiday shutdown. If it is a design change that requires modification of a part it will have to pass the business risk/reward requirements and could take a long time to implement, if ever.

Bottom line, enjoy the car as I am, regardless of the tick. Mine is the only Z06 I have heard that has it, so you chances of getting a noisy one are probably low. Even if you do get a loud one, GM is not requiring the fix and you can drive it until more is known. I have 3,200 miles on mine. I plan to get the PICO Scope measurements taken in the next week or so to get the repair process started.

348SStb

Update:

I asked my man at Chevrolet today to reach out to the regional GM rep on this issue. I was told in writing after some time that he was successful in speaking to the rep and he was told the engines for Z06 are not “banked,” or assembled in advance. They are made by hand “on time” for delivery. It would have been better to have more information like whether they are implementing a fix during assembly but information about that topic was not given to me in the description of the rep’s response.

But if we trust this, then there’s no stockpile of engines waiting to be used.

(With that being said, if they’re producing around 80 Z06s per day I’m not sure where the labor and man hours are available to assemble engines on the spot by hand for all those deliveries.)

adamsocb

Not stockpiling, just normal engine build to car assembly lag, still called “just in time.” Per the GM LT6 seminar last year “Every LT6 is shipped to a local dyno facility for a 20 minute run-in procedure.” That alone likely takes a week or so. Add to that a few days for scheduling and a few shifts buffer to avoid line shutdowns for an engine supply hiccup and it’s pretty easy to get to two weeks between engine and car assembly.

I have tried without success to find the “build date” of my LT6 engine. I suppose the engines could be completed as recently as a week before car assembly, but that would be really fast.

As for daily Z06 production, the average has been running 40-45 a day for the last several months. That is still a high throughput for the hand build engine shop. Early reports said the LT6 took ~3 hrs to assemble. I remember reading somewhere they had to slow that down some. At two engines per shift per builder they would need something like 20-25 engine specialists to keep up with a 40-45 car per day rate.

AzDave47

They started out with12 trained engine builders and were looking to build that to 24, I believe. I have not gone thru the "who built your engine" thread to count how many different engine builders have been listed so far, but you could do that and report back in this thread.

thebishman

One would think that during the 20 minute dyno run the harmonics of each individual engine could easily be measured, and if the ‘ticking noise’ is noted, that engine isn’t sent to the assembly line until the fix had transpired.

adamsocb

I agree, which is why I think either:

1. The noise develops with longer loaded run time
2. There something to do with installation in the car like added accessories, or mounting stress
3. They were not measuring/listening for this specific noise and vibration, easy to add

Redc8z06

Maybe but most likely the engine is tested in a sealed room with the technician outside the room so probably can't hear it and they probably didn't do a harmonics test procedure until now.