Gears & Axles Driveshafts | Rearends | Differentials | Gears | 12 Bolt | 9 Inch | Dana

Help with gear selection

Thread Tools
 
Search this Thread
 
Old Feb 1, 2016 | 02:59 PM
  #1  
SwampWS6's Avatar
Thread Starter
TECH Fanatic
iTrader: (7)
 
Joined: Apr 2013
Posts: 1,077
Likes: 1
From: Ballwin, MO
Default Help with gear selection

So have been doing some reading and have came to a bump in the road. I plan on purchasing a S60. Things to consider is that the tracks around the STL area are mostly 8th mile. Gateway is the only 1/4 track around and also the closest.

I have been using online calculators to figure out what gear to go with. The calculator pretty much told me I need between a 3:99-4:01 gear to trap 130mph-140mph on a 28" tire. I think thats kinda high! Especially with a Th400 first gear being 2:48 IIRC.

Most people I ask, tell me 3:54s will be fine. But by doing the math, it seems that the 3:54s are out of the question.

The specs are in the sig. I am leaning towards 3:73s but I think anything over 4:00 is too high. Car will be a 75% track car and a 25% street car. Im just lost on what to choose between the 3 options 3:54, 3:73 and 4:10.
Reply
Old Feb 1, 2016 | 03:12 PM
  #2  
panic's Avatar
Staging Lane
 
Joined: Feb 2005
Posts: 97
Likes: 2
From: Lynbrook, NY
Default

3:54s will be fine

I think what they mean is that anything higher will become annoying at high cruising speed, while not reducing your 60 ft. by much.
What do you like for trap RPM?
I had a 3.91 axle in my DD, and the motor buzzed way too much for my taste - but it was still hard to launch without blowing off the tires.
Reply
Old Feb 1, 2016 | 03:32 PM
  #3  
SwampWS6's Avatar
Thread Starter
TECH Fanatic
iTrader: (7)
 
Joined: Apr 2013
Posts: 1,077
Likes: 1
From: Ballwin, MO
Default

Originally Posted by panic
3:54s will be fine


What do you like for trap RPM?
Not sure, car has never been down track. So I dont know how to accurately answer the question. I would guess by having a TH400 I would the between 6500-7000 maybe. I know my cams operating range is between 6400-6700rpm
Reply
Old Feb 1, 2016 | 04:49 PM
  #4  
panic's Avatar
Staging Lane
 
Joined: Feb 2005
Posts: 97
Likes: 2
From: Lynbrook, NY
Default

Speed = (.002975 X RPM X tire OD) / axle
Using 6,500 for safety: 153 mph
Reply
Old Feb 1, 2016 | 10:24 PM
  #5  
murphinator's Avatar
12 Second Club
iTrader: (2)
 
Joined: Sep 2009
Posts: 1,650
Likes: 1
From: southern Maine
Default

turbo cars like less gear that is why people are recommending the 354's well that and if its making a lot of power too steep a gear will keep you from being able to see potential on trap speeds. Ride the boost freight train lol.

For example Grand Nationals came with 342's and usually you don't see those guys even the fast ones change gears unless they need way more tire then they will change gear but it equals back out close to the same effective ratio when you figure in the tire rollouts effect on final gearing
Reply
Old Feb 1, 2016 | 10:50 PM
  #6  
panic's Avatar
Staging Lane
 
Joined: Feb 2005
Posts: 97
Likes: 2
From: Lynbrook, NY
Default

True - taller axle loads & spools the turbo sooner.
Reply
Old Feb 2, 2016 | 07:19 AM
  #7  
SwampWS6's Avatar
Thread Starter
TECH Fanatic
iTrader: (7)
 
Joined: Apr 2013
Posts: 1,077
Likes: 1
From: Ballwin, MO
Default

Originally Posted by panic
Speed = (.002975 X RPM X tire OD) / axle
Using 6,500 for safety: 153 mph
Cool, So with your math above:
145= (.002975 X 6500X 28) / 3.73

145 doesnt seem like too bad of a trap speed.
Reply
Old Feb 2, 2016 | 07:26 AM
  #8  
SwampWS6's Avatar
Thread Starter
TECH Fanatic
iTrader: (7)
 
Joined: Apr 2013
Posts: 1,077
Likes: 1
From: Ballwin, MO
Default

Originally Posted by murphinator
turbo cars like less gear that is why people are recommending the 354's well that and if its making a lot of power too steep a gear will keep you from being able to see potential on trap speeds. Ride the boost freight train lol.

For example Grand Nationals came with 342's and usually you don't see those guys even the fast ones change gears unless they need way more tire then they will change gear but it equals back out close to the same effective ratio when you figure in the tire rollouts effect on final gearing
Yes, I understand the theory but just by calculating it seems that 3:99+ seems like too steep of a gear. Now a friend of mine has 3:73 and runs 8:60s on a stock 6.0/317 setup. He makes good power but his car loves that gear! I think if he dropped the gear or raised it, he wouldn't ET as well.

Also, I'd like to ET as best as possible. trap speed is great and all, but having a high trap speed but a sucky ET kinda defeats the purpose to me.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Feb 2, 2016 | 09:14 AM
  #9  
panic's Avatar
Staging Lane
 
Joined: Feb 2005
Posts: 97
Likes: 2
From: Lynbrook, NY
Default

There's also some tire slip (1%?) and converter slip, how much depends on converter efficiency and stall (2 different factors).
Reply




All times are GMT -5. The time now is 11:07 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE