Gear Ratios - Pontiac GTO Forum
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post #1 of 18 (permalink) Old 02-27-2011, 10:47 AM Thread Starter
 
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Gear Ratios

First, let me say I have read the sticky 3 times, thouroughly.

Currently I am running 2.73 gears in my stock 68 GTO/400, with a 4 speed transmission. I am scheduled to get these gears swapped out in three weeks. I have already bought 3.73s, but after reading the sticky on Gear Ratios, I want to be able to drive it both on the highway and have some power in town, so I am changing directions and really think I want 3.23s or 3.55s. The problem with my current gears is that I own a muscle car and it will not smoke the ONE tire. (I have bought an EATON posi 3 series carrier to go with my new gears.)

My goal is not for the car to smoke both tires forever, but I would like for it to chirp them a little bit, and then set you back in your seat. (That is what a muscle car is right?) This car will not be raced, but it feels like a dog right now with these gears and I don't like it. If you have experience with these gears, and have an idea what effect they would have on this car, please help!
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post #2 of 18 (permalink) Old 02-27-2011, 11:00 AM
 
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Split the difference....3.36......3.55 is a little stiff for long highway trips, although it is a great gear ratio for a 4 speed GTO



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post #3 of 18 (permalink) Old 02-27-2011, 11:40 AM
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My favorite gear for a 4 speed GTO is a 3.23. My own 4 speed '65 has a 3.36, because that's the tallest gear I could use with my carrier. 3.36 gears are ok...mine cruises 65-70. That said, my heavy, low compression, TH400 '67 GTO convertible has a 2.56 limited slip and it FRIES the tires. Something is wrong with your tune or combo. Seriously wrong. The tallest gear Pontiac put in their 4 speed GTO's was the 3.08. A 2 series gear with a 4 speed isn't the greatest, so yeah, you should re-gear. But get the engine checked out!
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post #4 of 18 (permalink) Old 02-27-2011, 12:14 PM
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Last October I swapped out 4.10's for 3.55's. Car drives and tachs great. Plenty of power and get up and go.

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post #5 of 18 (permalink) Old 02-27-2011, 12:21 PM
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Originally Posted by dahd11 View Post
Currently I am running 2.73 gears in my stock 68 GTO/400, with a 4 speed transmission. ...

The problem with my current gears is that I own a muscle car and it will not smoke the ONE tire.
Have you tried this formula?
1) Depress clutch pedal
2) Select first gear
3) Tach to 3000-3500
4) Side-step clutch pedal and simultaneously...
5) ...Bury the loud pedal



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post #6 of 18 (permalink) Old 02-27-2011, 12:31 PM
 
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I have a 3.55 on mine and it will cook the tires at the drop of a hat. It's great for crusin' around town or going on a country cruise. 2500 rpm at about 50-55 mph. rpm's do get a little high on the interstate though, 3500-4000 rpm @ 70-80 mph. I have a TH400 3-spd auto. trans so my set up is differant than yours. Sometimes I wish that I did have a higher gear, like a 2.93 mabe, because gas is starting getting expensive again. Hope this helped.
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post #7 of 18 (permalink) Old 02-27-2011, 01:13 PM Thread Starter
 
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BearGFR, you are right on. I baby all of my cars, and would feel guilty popping the clutch. My friends insist I do, but it is my baby... I am almost 100% certain it would light them up like that, but I don't want to do it that way. And frying my tires off is not what I want either.
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post #8 of 18 (permalink) Old 02-27-2011, 03:17 PM
 
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with GeeTee check your tune, that car should not have a problem barking the tires from a get even with the tall gear.
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post #9 of 18 (permalink) Old 02-27-2011, 04:59 PM
 
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Richmond gear has a fun calculator you can play with. Give it a speed and rpm it will calculate gear ratio. You need to know the diameter of your rear tires.

RICHMOND Street Performance Calculator
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post #10 of 18 (permalink) Old 02-27-2011, 06:04 PM
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Originally Posted by dahd11 View Post
BearGFR, you are right on. I baby all of my cars, and would feel guilty popping the clutch. My friends insist I do, but it is my baby... I am almost 100% certain it would light them up like that, but I don't want to do it that way. And frying my tires off is not what I want either.
Ohhhh tayyy... I wasn't advocating the procedure, necessarily - just offering a solution. I'd have a tough time doing that on a regular basis myself.

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