smw_zo6

Today I purchased a 2008, one owner Z06 with 12K miles. It looks flawless and all original. I took it on a 140 mile shake down drive. I bought the car from a dealership which took it in as a trade in for a new C8 Z06. My question is about the LS7 in stock form. How well does it drive in 6th gear doing 70 - 80mph. When driving my car it seems to be lugging a bit at 70 / 1500 rpm. The exhaust has a loud resonance 1500 - 1800 rpm. In fact it did not seem to want to hold that speed without additional throttle. I realize that this is crazy low rpm but for normal freeway speeds 60 - 80 the car seemed to prefer 5th gear. Is this normal? I am wondering if the car might have a cam? I don't have any history on the car. I may have falsely assumed that dealer trade-in = stock which is where I preferred to start.
Thanks,
Steve

Z.06

As a Z06 owner who has owned his car from new(museum delivery) and for the last 11 years in a slightly modified form, I would believe that your car probably has a mild aftermarket camshaft and an aftermarket tune. I would take it back to the service department of the selling dealership and ask them to certify that the ECM tune is legal for your Z06 in California. A stock tune and camshaft will have no problems with running smoothly at 70 mph/1500 rpm in 6th gear.on a level highway. I do think your car has had a camshaft change. Not to worry, my 55k mi Z06 is on its 3rd camshaft.

Scotthmt

6th gear with stock 3.42’s sucks under 82mph, lugs annoyingly. 15-1800 is the worst drone rpm.

smw_zo6

This was my intuition. I expect that the car would run reasonably at freeway speeds if not totally happy.

smw_zo6

That matches what I am experiencing. By 2000 rpm it seems very happy.

449er

Does your car have the NPP exhaust flaps? At 1,800 rpms, the exhaust valves would be closed and you should have no drone....Did all ZO6'S have NPP or was that an option in certain years?

Spaceme1117

If the car has the active exhaust (NPP) and is stock, check to see if there is the fuse in the passenger side footwell fuse panel. A common mod is to remove the fuse and keep the NPP valves open for more exhaust noise. This would also cause a lot of drone on the highway.

rocsvette

C6 Z06 all had NPP exhaust and as mentioned previously, some owners pulled the fuse to leave the exhaust “open” and at under 2000rpm the exhaust will drone. You can put an electronic control on that fuse operated by a small remote which allows you to open and close the exhaust as you like. Normally at low rpm the exhaust does not open in stock form. There is also a toggle switch you can install on the gearshift (actually a replacement ****) that allows you to manually open and close the exhaust bypass valves. One other item to check, by the firewall, drivers side rear of engine there is a vacuum line that goes to the exhaust solenoid in the rear. If that hose touches the engine it will melt and kill the vacuum which opens the exhaust. And yes I had that and had to drive from VIR to Bowling Green with that drone.

Nowanker

Should be zero issues driving 70 in 6th. 60 on a level road should be no problem either.
.If it has a cam and a tune, that's a different story. In CA, the seller is liable for smog compliance if there's any issue with legality.
They would have certified it before the sale...
Open exhaust flaps WILL cause that nasty highway drone regardless.

smw_zo6

Thanks for all the replies. It sounds like there may be separate issues. I have a fob for the NPP so I need to look at the fuse and try turning it off. It is possible that the noise resonance is exadurating my perception of the poor performance at 70 mph. That said even a slightly downhill section at 70, the engine feels off. The other obvious thing is to drive it some more.

Lights ZR1

The fob for the NPP is probably a Mild2Wild unit. Also sounds like you have a mild cam and a tune that isn't refined.

The thread makes me glad for the 0.68 6th in the MH3 gearset. 70 mph is 2,050 rpm!

niphilli2

Sixth gear is basically a double overdrive gear so yes it lugs the engine. Generally though the stock LS7 has so much low end torque it still picks up speed at WOT in sixth gear at 60 MPH.

if there is a smooth pull (and no jerking/bucking) and you can go WOT at 60 in sixth while picking up speed, then it’s probably in your head. Unless of course you have driven a double overdrive manual before and it just feels off.

id suspect your exhaust valves are set to open; the stock exhaust will drone as you describe with the flaps open at low RPM

Hib Halverson

A stock LS7 that's in good condition would run in 6th at 70-80mph with no problem

If the exhaust drones, it is likely to have an aftermarket exhaust behind the cats.

What's the idle speed and quality?

Z.06

So just to please me and make yourself look like an idiot, please confirm the road speed that your Z06 is going at 2000 rpm in 6th gear. Apologies will be accepted. I am confirming that my Z06, the second Z06 for me is going pretty fast in 6th gear at 2000 rpm.

Z.06

Well this is not true at all, and I have owned my 2008Z06 since new in 2008. It was a museum delivery car.

tommyc6z06

Z06 speed/gear calculator
https://xse.com/gearcalculator?title...rofile=&wheel=

tommyc6z06

I'll add, that it seems easy to almost inadvertantly lug these cars in 6th, as highway speeds drop with the ebb and flow of traffic.
I wonder if some of LS7 issues are not exacerbated by weird harmonics that may occur when the engines may be run down a bit low in such situations. I find myself often dropping to 5th, even if the car is capable of carrying 6th at times, Just a thought...

smw_zo6

Sorry but your are reading something into my reply something I did not say. My comment was to the the previous poster and droning of the exhaust at 1500-1800 rpm. My engine and exhaust are happier at 2000 rpm. 6th gear was not part of that comment.

smw_zo6

I obviously need to drive my car more but this echos my first impressions.

smw_zo6

I will test this out this weekend. I suspect you are right on the money. My C5 Z06 is geared lower so my expectations might be off. I have not driven a double overdrive manual so your suspicion is probably correct, "in your head".