no pumps around me are 91. in illinois almost every gas pump is 87, 89, 93

 

That’s pretty good in town I’d get 13 and 50/50 18ish.

 

question. I found a certified 2007 with 66k miles for 13986. Seem like a fair price, and if its certified, does that mean it already comes with the warranty?

 

Sorry, I meant to say 91 is the recommended minimum.

The 5-year/100,000-mile* powertrain warranty was introduced with the 2007 model year. So yes, that '07 will have that coverage. What the certified used program does is provide that same powertrain warranty to the '05s and '06s as well as provide a 12-month/12,000-mile bumper to bumper warranty on the used vehicle.

*Whichever comes first from original in-service date, 2005 through 2011 models only. Some 2005 models will not be eligible based on their in-service date. See your dealer for limited warranty details.

 

Quoted for truth.

This is completely disingenuous and inaccurate advice. The fact is, the problems we have with our transmissions have little to do with modifications. There are many people on here with "CAI/exhaust" who've had transmission failures. Indeed, there are plenty of 100% stock LS4s that have failed. I'm on #3 myself, with only a muffler delete and a Diablew tune. In fact, the last failure came with a stock tune installed. For the record, I've run a mobile-home sized trans cooler since I bought the car at 30k miles.

The fact is, these transmissions fail because of design and execution compromises made by GM in the name of comfort and cost-cutting. They simply can't reliably handle the power of even a stock LS4. I seriously suggest you do a search of the LS4 section for transmission problems, going back maybe 6 months or so and see for yourself the shear number of failures and/or problems.

Very true on the mileage. These cars have very loose converters in them, and they suck gasoline in town like a jet fighter on afterburner. When you can get out on the highway so the converter can stay locked and the motor goes into 4-cylinder mode, it is possible to see 27-30 MPG. If you drive mostly in town, then the mileage won't be much better than your truck.

After driving around with my Aeroforce Interceptor scan gauge attached to my car for the better part of the past year, I can tell you that I would NEVER run anything less than 91 octane fuel, and would put 92 or 93 in it, if available. On the stock tune with 91 octane, I would see 5-8 degrees of knock retard with even the slightest load, even in 40 degree ambient temperatures. In the summer, I would occasionally see a couple of degrees of KR while cruising. Keep in mind, I have real-time knock data displayed every moment the car is running. I can tell by the KR display when I have a bad tank of gas or if I accidentally got 87 or 89 octane. Now, after I got my DiabLew tune from 06MonteSS, 95% of my KR is gone. Unfortunately, only the 05-06 GXPs can be tuned by Lew, otherwise, you're buying an HPTuners unit.

Anytime you have KR, the knock causing it is doing damage to the engine. Yes, I know, the retarded timing is supposed to protect it, but over the years and miles, it adds up. Also, knock causes carbon build-up inside the combustion chambers and on the pistons, which can cause hot spots and make the motor even more susceptible to knock. It's a viscous cycle. Lastly, a lot of KR can hurt mileage. These engines run a lot of timing to get the mileage and power out of them, and if that timing is retarded often due to knock, your mileage and power will be reduced. The factory tune is also excessively lean, so the combination of the two factors is a recipe for lots of knock.

Sorry to be so long winded, but these are the main issues with the car. There are others like bad wheel-hub assemblies, flaky TPMS sensors, etc., but these could be expected with any car. The trans is the biggest risk, and the tune has the biggest impact on drivability.

If you do buy an LS4 car, I would strongly suggest budgeting for some trans work and a tune of some sort. I would contact Lew (06MonteSS) to discuss the ins and outs of a tune, as he's a great guy to work with. As for the transmission, I'm trying something a bit different to try and prevent mine from dying again. If you want more info, PM me. Or you can call Dave at Triple Edge Performance and learn first hand how badly compromised our trannies are.

Anyway, good luck with your decision.

 

damn, I guess I should look for a different vehicle then. Thats a damn shame about the trans, but its really turning me off. I want a vehicle I can get in and drive without fear. With my f-bodies, it was the 10 bolt, with my Lightning, its the rods breaking under boost, and with the GXP it'd be another trans. Doesn't sound like something I want to deal with.

 

Sorry to be a buzz-kill, man.

But please, don't just take my word for it. Do the search I suggested on this site and see for yourself.

For the sake of balance, these are nice, comfortable cruising cars. And the GXPs are exceptional handlers right out of the box for cars their size.

It's just that you gotta take the bad with the good.

 

its not a buzz kill, its the truth, and I'm glad for it. I love the interiors on these cars, the power on tap, etc. I'm just gonna look into what it would take with the trans to keep it together. Maybe I can get the car, and then have the trans beefed with my tax return.

 

For the record, I'm probably about to be on my third, but there are still more "non-failed" transes than failed transes. I drive mine hard and rough every day and always use TapShift, shifting too high and downshifting too soon. I also drag race and Autocross it.

If you like it and have driven other things, then buy it, just keep in the back of your mind, that there is a possibility the trans may fail, doesn't mean it will.

 

where can I find transmission upgrades? I've been searching the forum and google for the past 20 minutes and can't find ****.

 

Dave at Triple Edge Performance

 

Thanks. I sent TEP an e-mail stating how I just want a trans that can handle DD duties and the occasional pedal to the floor with no dragstrip time. I'll see what he says. I figure if I buy certified used, then I'll just pray the trans doesn't break, but if it does, then I'll get it replaced under warranty until I can afford a built one.

 

More "non-failed transes than failed transes" isn't saying much, is it?

You know, I would have thought that 6 months ago, but as time goes on, and more and more people are posting problems as their miles increase, I'm starting to believe that the failure rate at 100k miles is higher than 50%. I have no data to support this, but it sure seems like there's a new tranny issue every week.

And even if the failure rate is lower, say 25-35% range @100k miles, it's still a 1-in-3 or 1-in-4 chance, which in my opinion, is unacceptably high for such a relatively pricey and new car.

 

Bingo!

PM returned

 

Dude. Keep.Your. Truck.

 

Don't want it. Has 138k, the interior is cheap, too tempting to modify. I can't afford a built motor in the Lightning, so doing any other mod is pointless. Its just not what I thought it'd be. I traded in my trans am for it, and regretted it within months. The gas is just horrendous. I want to get out of the car modifying scene and just drive something comfortable, powerful, and cheaper monthly than my truck (truck is 300, I can get a GXP finance for less and with a warranty). I have 3 semesters left of school, then once I find a career, I'm going to save for a house and work on my MBA. I guess right now I'm in my "grow up" phase until I can provide a decent living for myself, and then I'll get back into cars once I have real money to play with. Right now, its simply irresponsible on my part if I keep modifying **** to the extent that I want to.

 

PM'd back atcha.

 

well said and it is a jagged little pill to swallow when all of a sudden you have to be a grown up about things i know i was pissed but these arent bad cars all in all i have own 3 w-body cars 2 were supercharged and never had anything major go wrong but like any thing man made you got the good and the bad

 

Cars are my passion, but the thought of the extra cash in my pocket after the thousands blown on my past f-bodies and whatnot, it just makes the most sense. I'll be back in the game within a few years. Thats why I want a V8, still gives me the grunt to keep me sane. And with the LS4 having little to no aftermarket, makes it even better.

 

They dont handle to bad either but there is enough aftermarket to have fun with