Thread: LS4

Also a GXP owner. that's awesome that you ran a 13.85. I have a buddy with a brand new Cobalt SS/TC that really wants a piece of me as soon as ORP opens in the spring. I think this car can take him with a good launch and seeing that I want to put 18x9" rims and 275/40-18 tires with +20-24 offset so I still have clearance. As far as if the car totally hooked up... You would detonate the tranny. If you didn't FTW!!!! lol

well guys....im new here now too....and reading all that you have is very interesting....as far as the conversion or swap from the 6 to the 8....not a bad swap if you have the laboring hands and the money to do so....get ready for a lot of lights in your face...its like doing a brain surgery plus the heart...lol....the LS4 if you dont know is the same engine they use in the silverado.....only diff. is that the silverado is cast iron and the GXP block is all aluminum....just a tid bit...so more heat...so you would need to run a diff therm. as far as fitting in your housing....it will work....and the combo of aluminum housing and the aluminum crate would be quite the weight reduction...shed some fat....great idea. not knocking it at all, but, do consider that besides the reduction in weight, your now running into the same tunning issues as all of us...a lot of people say this is a new motor...yes and no...its a new version for the GXP trim only...and been moded for those purposes...but it is still the old silverado motor...I would go out on a lim and say...lets try checking for parts and upgrades for the truck motor...i bet you would be suprised...a lot of the upgrades on the truck motors will go with our cars...the V8 at least...SAME MOTOR...diff PCM and gearing...but minus that...the parts are there...so give that a shot...just a thought though...havent looked yet...as far as further weight reduction goes...the GXP trim has a chasis that is light weight anyways...exclusive to the GXP and no other GP model...not the GT, GTP or SE...so less weight is what you would get with the combo of engine and housing with the horsepower...so you would simply get gains from power to wgt. ratio....but you would be suprised on the gross wgt. the GXP has vs. the GT you have...look it up...we...put it this way the GTO is 100lbs. heavier than the GXP trim...not being cockie...just stating the facts for your indeavor for your sleeper...nifty lil project though...

going just lil further in the heat aspect....the aluminum block will get hotter, u guys know that much...so if your doing a swap...it would be ok as long as you use the LS4 therm....but in combo with all the mods...not a single person has said anything about the heat issue...no one has done enough to the GXP to really take the test of time that these limited mods that are avail. do to our gals not having a high demand...so we need to keep em cool...and...the pontiac tranny is not too bad at all...its fast of the tooth and quick to respond...its peppy....just the thing we all love about a PONTIAC...you hear about the horror stories of tranny blow outs from the line and hard shifting while racing on the street or on the track...all of these are over time....its the abuse they are getting.......simply from getting too hot...and if you have plans on installing a PCM module or changing any shift points with a tune or flash from a super chips etc...then just simply do what is common since for any street racer....keep the tranny cool...get a kit...you will def. get one with a power adder...its part of it...so get those tranny's cool...the GXP...the LS4 I should say...has been tweaked a wee anyway to handle the demand the engine requires for it...its a solid...just keep it cool...if you notice, it will get hot on you anyways just running factory....so good recommendation...get a tranny cool kit with any aftermarket upgrade besides a CAI....that is my number one right there...and by the way...the 07 is a collector item.....well limited...my 08 made up the majority of the GXP's produced....it was the largest production yr. for them...but, the last...so it keeps some stripes there...all in all there has been just under 15,000 of these kids produced....but good for the 07....

oh yeah....panther im clear on the monte and impala ss....hey, i was looking at a throttle body spacer....TBS from Power AIR...AIR AID...they have one for the LS4 for a Silverado...i sent them a request...asking them to let me know if we can use it for our LS4........I dont see why not....

so i found it...and i called JEGS, talked to a tech....he advised that they just dont have a thing or a clue where to start with the LS4 for the GXP....and he couldnt advise if the Silverado spacer would work due to diff. set up of the air box etc...he stated if it works they would of put it there in their invetory, due to the 05-06 having some yrs on it and being out there in the market for right now.....he did say the PCM from JET and i looked at that and already had that planned, along with their Mass AIR FLOW SENSOR...do an inquiry on the GXP on the website...Comp CAMS has a lot of stuff for our DOD engines...CAM, rockers, springs....etc...

Im still doin research on the LS4 on my 06 GXP and it is tuff finding people that have modded these cars (same with the bonneville gxp). Id like to pick there brain to ask what worked well with modding these cars and what to avoid/watch for.

and as for a thermostat, when modding these things what kinda thermostat should one get?

Originally Posted by Reptile

Honestly??? Transmissions just don't go bad one right after the other like that. I work at a dealership too...and it just doesn't happen.

Don't wanna call him a liar or anything....but seriously if they all had that problem, there would be one HUGE recall.
You gotta realize...a dealer has to have suspicions when a car comes in for FIVE transmissions within 50k miles.
I'd be looking into some issue with the car itself...be it a PCM problem with transmission settings.

Perhaps Dave would be able to shed some light on the subject.

I'm no rocket scientist but I'll bet some of the trans problems have to do with the paddle shifters. A few years ago when Dodge first put the autostick feature in their 300m's & Intrepids I had a couple of buddies who bought them & they had nothing but trouble out if their respective vehicles. Mostly all trans related.BTW they swore by their autostick, I think it made them feel like Indy drivers or something.I have 39k on my GXP & haven't had a hicup from my trans yet(knock on wood).That doesn't mean it won't happen in the future-BUT-I do not use this feature. I've never been a fan of the paddle shifters.