(04' 5at)
Hey there, my car is kind of a weird one so I'll start with when I bought it, the guy advertised it as a sport coupe, and it had a few SC features, like the aero spoiler, but no other aero mods, no side skirts, no front lip. It has the SC owners manual, and has all the electronical SC knickknacks as far as I know.
BUT, the diff I'm not really sure of, because the VIN goes to a base model car, that has an open diff, but in the engine bay on the little plaque on the passenger inner fender it says it has an RC33 diff, which I only thought came in the sport model, and it was an LSD, so what really is my car?

 

Jack up the rear end and put the car on jackstands and the transmission in neutral position. Hold one tire steady (chock it with the jack or something if you don't have a second person) now go spin the other tire. Does it spin freely, if so then open diff. Does it spin but with a LOT of resistance, VLSD.

To find out your gear ratio make a match mark with a sharpie on the driveline yoke to diff housing, and a matchmark across the axle to diff housing. Now start spinning the driveline by hand and count how many revolutions it takes to make the axle do exactly 1 complete turn.

Should be 3.5 turns for the VLSD, 3.3 turns for the open diff, but there are also 3.7 and 3.9 gear ratios from later G/Z that can be swapped in along with plentiful aftermarket support so this way you know for sure what your gear ratio actually is.

You could also pull the diff cover (drain gear oil first) and just look at the internals to see what it's got (won't tell you gear ratio but you can visibly see the difference between open, VLSD, or helical/clutch LSD) but you will need to permatex Ultra Grey RTV the cover back on.

You could also just get out in an empty parking lot or stretch of road and lay down some rubber (turn VDC off), then get out and look at the tire tracks, open will be one side burning out the other side not, VLSD will be two stripes with one side a little heavier than the other, clutch/helical LSD will be pretty even stripes. Again this won't tell you gear ratio.

Swapping in the 3.5 VLSD was a common upgrade to the 5AT cars, more aggressive gear ratio means faster acceleration but higher highway cruising rpm.

 

They were all called "Sport Coupe" for '04. There was no separate "sport" model as there was for '06-'07. The aero lip was a separate option and not an indicator of anything else. Automatics with the Performance Tire and Wheel package got the VLSD, 18" wheels w/ performance tires, and the silver (titanium) colored climate control/radio trim. As for the VIN designator I'm fairly certain G35s are either considered "base" or "X", so all '04 coupes are considered "base" in that regards, no matter the options.

 

That's correct, "base" just means "not AWD".

 

Couldn't we just tell by the way it says "RC33" or not? Since I don't want to drive it during the winter and it's parked in the garage that doesn't have the jack in it atm. Just trying to learn about my car during the winter since I can't really drive it.

 

That's probably just a casting number for the housing itself. The easiest way by far is to jack up the rear (the differential is the service jack point) and have one person hold one tire steady while you try to spin the other tire.

 

Preeeeetty sure it has an LSD, because when my father and I were putting on my exhaust, he held one wheel still and I could hardly turn the other wheel.
But how the heck does my car have an LSD? It doesnt have the performance wheel tire package, none of the suspension upgrades, and not even the brakes? Nothing on the outside tells me it has it.

 

A lot of those identifiers may have been removed or added during the last 15 years by previous owners.

Does it have aluminum pedals for the gas/brakes? That's something that people typically wouldn't be changing, if it has the aluminum pedal covers then it had the sport suspension package. Also what color thread/stitching on the steering wheel, if it's orange stitching then it was a sport suspension package. This also included the 19" wheels (something that's easily removed) and the VLSD (something that's also pretty easily removed, but usually only if it's being upgraded to something better).

If it has a factory rear spoiler that was only an option you could add onto a car that already had the sport suspension package, however that's something that could also easily be swapped later with one that either does or does not have a spoiler.

You can't visually tell the difference in the sway bars, they are the same outer diameter sport and non-sport so the bushings are the same, when you cut them open the non sport sway bar is 5mm thick, the sport bar is 7mm thick.

Springs however CAN be identified visually to at least determine if you have the early model or the revised springs. Look for large painted color dots on the spring. You will probably need to use some brake cleaner and a rag to find them. The rear springs were the only thing that changed, 3 red dots means the unrevised, 2 dots and 1 purple dot (the purple dot is on a different coil) means the stiffer/revised springs.

If it has the 2red and 1purple those springs were only installed on the sport suspension package with the 19" wheels. But again, swapping springs was a VERY common thing to do, especially in the rear since it's so simple to do.

 

Cleric, remember that the OP has a MY 2004. The sport stitching, aluminum/sport pedals, and 19" wheels were not available on '03-'04s, regardless of package. I'm pretty sure the stitching and pedals started with MY '06 (Sport package only). I forget if the 19" Rays were first available for MY '05 or '06.

I forgot to add that the center console color would be telling on an AT equipped car. The "titanium" colored console was a component of the "Performance Tire and Wheel Package".

 

Ahh yeah I thought I was looking at a 2004 brochure but apparently it wasn't.

Just found an actual 2004 brochure, ignore the orange steering wheel sticking, aluminum pedals, and 19" wheels.

The spoiler things still applies and like Mike was saying the titanium-tinted interior trim.

They also had 7 spoke 18" wheels but since wheels are so easy to swap I generally don't use that as a real identifier.

 

So my car has the stock 6 spokes, the spoiler, and I think the titanium bezel or whatever, but everything on the car right now is exactly how it came out of the dealership new in florida. It was a grandpa car so he never added anything onto it, but he said that they added the spoiler onto it at the dealer when he bought it.

 

The spoiler could also be added as a dealer accessory on it's own though, which is why I didn't use it to determine which package it had. The 6-spokes aren't the wheels that came in the performance package though, as Cleric pointed out those would be the 18" 7-spokes. The console is easy enough to figure out - is your center stack/console silver or does it match the dashboard?

 

It matches the dashboard, I always thought people were talking about the metal trim piece that goes across the middle between the dash and... lower dash?

 

The dealership never plugged in the rear spoiler light either, or it went out, cause neither the spoiler nor the rear window taillight turns on when braking.

 

So, in total, my car has from the dealership when it was brand new:

• An LSD from the Performance Wheel and Tire Package, but no performance wheels or tires, or titanium center console.
• A spoiler, but no spoiler lights nor rear window lights, or any other aero knick-knacks.
• Stock 6 spokes from non-performance package, on a car with the LSD from the package. (Keep in mind the wheels were not swapped out)

My best guess of what it is is a base model car, but the dealer decided to swap the LSD into it, throw a spoiler on it, and give the "sport coupe" manual to the original owner, and the owner advertised it as a "sport coupe" car, cause he thought it was one. That sound about right?