Gears...splain them to me
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Gears...splain them to me
my RPO code list says I have the GU6 (3.42 axle ratio) with a MM6, MN6
I see a lot of mods for changing gears. Why are folks changing gears? Is it mainly for drag racing applications?
I see the other choices for gears are the GU2 (2.73), G90 (3.15), and the G92 (performance ratio).
My understanding of basic gearing is that a 4.10 will get you to redline quicker but won't allow as much top speed
What is the scope on gearing for the C5?
My application is mostly road racing. Even though I've got about 400 rwhp, it just seems real lazy until about 4k rpm's (could be partially my cam selection also).
Maybe I've grown too used to 400 rwhp but it seems like the car should be faster, so i'm wanting to learn more about gearing.
I see a lot of mods for changing gears. Why are folks changing gears? Is it mainly for drag racing applications?
I see the other choices for gears are the GU2 (2.73), G90 (3.15), and the G92 (performance ratio).
My understanding of basic gearing is that a 4.10 will get you to redline quicker but won't allow as much top speed
What is the scope on gearing for the C5?
My application is mostly road racing. Even though I've got about 400 rwhp, it just seems real lazy until about 4k rpm's (could be partially my cam selection also).
Maybe I've grown too used to 400 rwhp but it seems like the car should be faster, so i'm wanting to learn more about gearing.
Drifting
Joined: Sep 2001
Posts: 1,421
Likes: 3
From: Memphis Tn
Re: Gears...splain them to me (Gary2KC5)
You just need to go to a stage II H/C setup, your gear is just fine, you wouldn't want a 3:73 or 4:10 on a circle track, it's drag strip only and you'd lose your top end,and 2:73 or 3:15 would make your problem worse, since you said it doesn't get up and go til about 4000 rpm, you can't even spin a 2:73 gear. You've got the hp, you just need to get the rpm's to jump up and fall back down faster so you can shift quicker. Reading your mod list you've got the intake and exhausts covered, it looks like your heads are the culprit. You might want to upgrade to a St II H/C setup with possibly some larger valves. I think your heads are choking it.
Hope this helps.
[Modified by ScreaminDemon, 1:20 AM 5/1/2003]
[Modified by ScreaminDemon, 1:24 AM 5/1/2003]
Hope this helps.
[Modified by ScreaminDemon, 1:20 AM 5/1/2003]
[Modified by ScreaminDemon, 1:24 AM 5/1/2003]
Racer
Joined: Sep 2002
Posts: 483
Likes: 0
From: Austin Tx
Re: Gears...splain them to me (Gary2KC5)
Gears:
An engine produces TQ, TQ gets multiplied by the transmission, and then gets multiplied (again) by the differential. The rear axel TQ is then divided by the rolling radius of the rear tire to arrive at thrust.
Thrust is a force. Thrust divided by the mass (weight) of the car determines the potential acceleration (a = f/M or f=M*a). If the rear tires are not slipping then the car can acclerate as described.
So by using numerically higher gear-ratio or differential ratios, you achieve more thrust at the rear wheels. Thrust causes acceleration, more thrust causes more acceleration.
An engine produces TQ, TQ gets multiplied by the transmission, and then gets multiplied (again) by the differential. The rear axel TQ is then divided by the rolling radius of the rear tire to arrive at thrust.
Thrust is a force. Thrust divided by the mass (weight) of the car determines the potential acceleration (a = f/M or f=M*a). If the rear tires are not slipping then the car can acclerate as described.
So by using numerically higher gear-ratio or differential ratios, you achieve more thrust at the rear wheels. Thrust causes acceleration, more thrust causes more acceleration.
Le Mans Master
Joined: Dec 2000
Posts: 9,919
Likes: 1,880
From: Hot Springs AR
Re: Gears...splain them to me (Gary2KC5)
Maybe I've grown too used to 400 rwhp but it seems like the car should be faster, so i'm wanting to learn more about gearing.
Now, the MN12 gearbox could help you out, because it has gears that are not only a bit higher numerically, but also closer together. That way you could keep the revs closer to your peak.
Hope this helps, and have a good one,
Mike
Burning Brakes
Joined: Jun 2002
Posts: 872
Likes: 0
Re: Gears...splain them to me (Mitch Alsup)
Gears:
An engine produces TQ, TQ gets multiplied by the transmission, and then gets multiplied (again) by the differential. The rear axel TQ is then divided by the rolling radius of the rear tire to arrive at thrust.
Thrust is a force. Thrust divided by the mass (weight) of the car determines the potential acceleration (a = f/M or f=M*a). If the rear tires are not slipping then the car can acclerate as described.
So by using numerically higher gear-ratio or differential ratios, you achieve more thrust at the rear wheels. Thrust causes acceleration, more thrust causes more acceleration.
An engine produces TQ, TQ gets multiplied by the transmission, and then gets multiplied (again) by the differential. The rear axel TQ is then divided by the rolling radius of the rear tire to arrive at thrust.
Thrust is a force. Thrust divided by the mass (weight) of the car determines the potential acceleration (a = f/M or f=M*a). If the rear tires are not slipping then the car can acclerate as described.
So by using numerically higher gear-ratio or differential ratios, you achieve more thrust at the rear wheels. Thrust causes acceleration, more thrust causes more acceleration.
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Re: Gears...splain them to me (IJustSmile)
There should be an RPO code list somewhere (mine is on the glovebox door) that lists all the RPO codes. see my 1st post for the RPO codes for the different gear ratios (except the "performance" gears).
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Re: Gears...splain them to me (IJustSmile)
How do I find out what rearend gears and trans. are in my 99 Vert.? I bought it used so I don't have the original paperwork.
Drifting
Joined: Sep 2001
Posts: 1,421
Likes: 3
From: Memphis Tn
Re: Gears...splain them to me (Gary2KC5)
The gear is not it. 3:42's are the most effecient for what the C5 was designed for in the first place, that's why it is standard in a stickshift. 2:73's and 3:15's would be wrong because you are looking for more bottom end and they are designed just for top end. 3:73's will kill your topend, but give you great bottom end. You only have St I heads and cam, and that's a small cam. You know you want to bump it up, why fight it? It's only money? haha Good luck
David
David
Burning Brakes
Joined: Oct 2001
Posts: 1,205
Likes: 0
From: Dallas City IL
Re: Gears...splain them to me (Gary2KC5)
Gary,
In your car, 3:73 will get you very similar Z06 gearing, w/o having the streach to 4th gear like the Z. Anything more than 3:73's would be drag only IMHO. But I think 3:73's could really benifit you on the road course. Also, as far as killing top end :rolleyes: How's 165mph and still pulling sound :D
In your car, 3:73 will get you very similar Z06 gearing, w/o having the streach to 4th gear like the Z. Anything more than 3:73's would be drag only IMHO. But I think 3:73's could really benifit you on the road course. Also, as far as killing top end :rolleyes: How's 165mph and still pulling sound :D
Drifting
Joined: Sep 2001
Posts: 1,421
Likes: 3
From: Memphis Tn
Re: Gears...splain them to me (Gary2KC5)
Just another note for the ratio. 3:42 rearend gear means the axle gear is making almost 3 1/2 turns (3.42) for each rotation of the drive shaft. 3:73 means the axle gear is making 3 and 3/4 turns for each rotation of the drive shaft. So you can see how as you reach top end the larger gear (numercally, because the gear is actually smaller with less teeth), will start costing you. Just the opposite with a 2:73 or 3:15, which runs like a snail off the line, but has a higher top end due to the smaller gear (numerically-but it is actually larger, with alot more teeth), capable of much higher speeds, Like the biggest sprocket on a 10 speed. Which is why the 3:42 is the best for circle track. I hope I didn't get to elementary, I'm tired and need to get some sleep! haha
Team Owner
Joined: Jul 2001
Posts: 21,404
Likes: 1,011
From: Various places in Southern California.
Re: Gears...splain them to me (ScreaminDemon)
Just another note for the ratio. 3:42 rearend gear means the axle gear is making almost 3 1/2 turns (3.42) for each rotation of the drive shaft. 3:73 means the axle gear is making 3 and 3/4 turns for each rotation of the drive shaft. So you can see how as you reach top end the larger gear (numercally, because the gear is actually smaller with less teeth), will start costing you. Just the opposite with a 2:73 or 3:15, which runs like a snail off the line, but has a higher top end due to the smaller gear (numerically-but it is actually larger, with alot more teeth), capable of much higher speeds, Like the biggest sprocket on a 10 speed. Which is why the 3:42 is the best for circle track. I hope I didn't get to elementary, I'm tired and need to get some sleep! haha
Drifting
Joined: Sep 2001
Posts: 1,421
Likes: 3
From: Memphis Tn
Re: Gears...splain them to me (Duck916)
Thanks for correcting me, I did say I was tired and needed some sleep! :lol: :lol: :lol: :lol: :lol: :lol: It's a trade off, bottom end or top end, or somewhere in the middle for circle track.
Le Mans Master
Joined: Apr 2001
Posts: 8,133
Likes: 144
From: Ex-SF Bay Area; now happily Denver area
Re: Gears...splain them to me (ScreaminDemon)
Thanks for correcting me, I did say I was tired and needed some sleep! :lol: :lol: :lol: :lol: :lol: :lol: It's a trade off, bottom end or top end, or somewhere in the middle for circle track.