For those guys with turboed or supercharged g coupes, do your gears go on by fast? more like fly by? Any of you guys change out your final ratio?

 

depends on what u want to do when u FI. Are u drag racing meaning u only need the gears for the 1/4 miles and nothing more OR u want it to race on the top end.

If u want top end gearings (freeway races) u want tall loong gears like the automatic 3.3 but your acceleration is slower and u fall out of boost faster when u shift.

If u want better 1/4 mile then u want shorter gears like the aftermarket 3.7 and the migthly 3.9 so u can quickly zoom each gear but dont expect to go pass ~135mph bc u will be riding redline and then BOOOM.

They both have their pros and cons.

 

unless you have plans to drive over 184mph or 198 mph for a rev up engine on the highway, I'd stay away from taller gears for the sheer sake of top end freeway driving

I'd actually go for the 3.9 final drive for highway running if you're ok with a top speed of 168mph for the 287hp engine and 179mph for the rev up engine. Just gotta get the power to do it and remove the 160mph speed limiter

drag racing with a turbo and shorter gears probably isn't the best idea unless you're running drag radials or slicks

 

ey sentry.. how u like ur 3.9?? do u have any times on the track??

 

how would 3.9 gearing get u top end spd? Those gears are soo short compare to the 3.3. that is why its good for 1/4 mile only where u dont see hi mph.

Like i said before if u use tall gears/ long gears (3.3) u will have slower acceleration and tend to drop down more in rpm when u shift compare to shorter gears. ie. with 3.3 final drive 80mph is at 3000rpm and with 3.5 final drive 80mph is at 3200mph. Therefore 3.9 final drive will have a higher rpm.

Longer gears arent that great for FI (short distances) bc it takes u longer to hit full boost compare to shorter gears. It's only good for top end where u are now able to stay in boost longer in 5-6 gear.

Best combo would be short 1-5 (faster acceleration) and long 6th to stay in boost and go up hi speed.

 

basically, I'm going to argue the complete opposite. I say that if you have a million hp engine, what you want is tall lower gears, and short higher gears to compensate for the air drag that exponentially increases at higher speeds

shorter lower gears and taller high gears is a good formula for a low powered car to compensate for it's lack of power by having shorter low gearing to help it's accelleration, then getting great gas mileage on the highway at higher speeds.


your top end will be stronger with the 3.9, but won't go as high of a top speed as the 3.3

Since I pretty much doubt anyone is going to really need their Z to go above 168mph for the 287hp engine and 179mph for the rev up engine, I'm going to say for 99% of people the 3.9 would be the better choice for high speed accelleration. I mean, unless you're going for a high speed record in the salt plains and have 600+whp - only then would the 3.3 be a good choice for high speed runs where you need to drive closer to 200mph.

the 3.3 might be able to eventually reach higher top speed, but will have less enthusiasm to get you to the 3.9's 168mph top speed. It might get you to 168mph, but it'll be a long slow process, where the 3.9 will feel like the car has plenty of power left but you just ran out of gears


now we're talking about transmission gearing instead of final drive gearing

a tall 6th gear means your higher end speed is going to suck hard. There needs to be a balance found between gearing and engine power. If you have a million hp engine, then tall gearing in general would be ok. But super tall gearing where your top gear is geared for 500mph, you're just not likely to reach 500mph. Maybe you'll reach 200-250mph, so having gearing that takes you to that speed is a better choice - assuming you have a strong enough engine to reach those speeds (700-1100whp)

BTW, in 6th gear as it is now, when you shift from 5th to 6th gear you're right around 5500 rpms. Last I checked 5500rpms and higher is well into the boost range on a turbo.

You might be in boost longer with a really tall 6th gear, but what good does that do you if your accelleration sucks? It's kinda pointless to go 0-140mph in 20 seconds then take 2 minutes to go 140-160mph for the sake of bragging how long your staying in boost. Even if you have a million hp where 6th gear can still accellerate you pretty well, then that just means your lower gears are WAY too short. Really you want your gearing to be fairly evenly spaced.

What you DO want though for optimum top speed performance is the next gear to progressively start you higher and higher in the rpm band. Most cars don't do that for the sake of gas mileage. The Z sorta does it but drastically tapers off.

What I mean is when you shift from 1st to 2nd at (6600rpm) redline, you end up at around 4500 rpms
then when you shift to 3rd, you're at 5000rpms,
shifting to 4th starts you at around 5500 rpms
shifting to 5th starts you at around 5550 rpms (this is where it starts tapering off)
shifting to 6th starts you at 5600 rpms

at higher speeds, you want to be at a higher hp in the powerband to maintain accelleration as much as possible which means on the Z you want to be closer to redline since the Z makes more hp at redline than earlier.


Most F1 race cars are tuboed and have lots of gears and each gear is very very short. If it was a benefit to have the gearing be taller to "stay in the boost" longer - they'd do it if it was faster. But atlas being at a higher rpm and staying at a higher rpm as much as possible with aggressive short gearing has yielded the fastest setup. If "staying in the boost" with tall gearing was paramount, we'd all be driving turbo diesal engines reving to a mighty 3000 rpms

the new Z06 is actually geared for 340mph, but can "only" reach 198. Now Chevy COULD channge their 5th and 6th gear ratios so that the car would go above 200mph - and trust me it'd do it. But Chevy knows that 198mph is still damn fast and probably less than .02% of the middle aged men who buy Z06's would ever attempt a top speed run to 198mph and want more. However everyone wants good gas mileage and no one wants to pay a gas guzler tax. So Chevy makes 5th and 6th gear really really tall since that'll make more people happy since most Z06's are street cars driven around town. Chevy would rather advertize 20/28mpg than 20/14 mpg. That engine would eat a LOT of gas if it wasn't for such tall gearing

http://www.f-body.org/gears/ is a great site btw


I like it, sorry don't have any times

 

Good info.


I have been happy with my 3.5 gears but have thought about going to the 3.3 many times. The Stillen has so much low end power it might help me.

 

help you how? sounds like you don't have good enough tires if you're doing it for traction reasons

 

only help would be better traction and better gas mileage...

the Stillen has a flat torque curve but a car will always accelerate faster (have more power to the wheels) at its power peak, not it's torque peak, assuming the torque only gradually declines (which it does past its peak in our cars).

 

Sentry when stated, "... shorter lower gears and taller high gears is a good formula for a low powered car to compensate for it's lack of power by having shorter low gearing to help it's accelleration, then getting great gas mileage on the highway at higher speeds. ...your top end will be stronger with the 3.9, but won't go as high of a top speed as the 3.3."
Aren't u basically agreeing with wat i said about having shorter 1-5 and longer 6th gear?

Turbos have lag, so why would we want longer gears when <3K rpm we have no pw (small turbo, small lag time)? Therefore, we need those shorter gears so we can accelerate faster to make up for the turbo lag. Now getting traction is another story.

The only reason why I suggested having a long 6th gear is in case anyone who is crazy enough to race a z06 up top can do so and at the same time save gas on the freeway.

Now of course if u going for top end pw against a vet you're going to need a HUGE turbo (small turbos run out of steam uptop). Therefore, once again taller gears will hurt u from the start bc now u wouldnt hit full boost until 5K rpm and taller gears dont accelerate as fast as shorter gears.

Like I mentioned earlier, it just depends on what u want the gears to do. Do u want to race only up to 1XX then the 3.9 final drive all the way (I dont have a 3.9 so I dont know how fast u can go before redlining). But if u want to compete with vets (and if u had a straight away long enough) up top to 200pmh then u need 3.3 or taller gears.

To recap, if u have a huge turbo, u want short gears in the beginning to compensate for the lag time and longer 6th gear to be able to get to 200mph.