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Old 12-28-2016, 11:23 PM
mtnbktrek mtnbktrek is offline
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Default what gear ratio? 3.36 or 3.55

i have 3.90 in there now this is for car in sig. 3.90 suck 1st gear is useless. i had 3.23 in there and it needed more but when it was 3.23 the car had a weak 400 in it. it now has the 462 listed in sig and is a powerhouse. so i dont go to the strip too often just 5-6 times a summer but doubt i can even run it because its a vert and i dont really want to put a roll bar in . i live in country 10 miles either direction i leave my driveway before i hit a town. im leaning toward the 3.36. just wondering if anybody has good actual knowledge on this. i tried a bunch of different calculators but they all come up with different answers. i have a new yukon posi i am installing as well

thx

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1968 LeMans Convertible - 462 w hydo roller comp cam forged flat tops- 6x-4 heads- performer intake - 800 cfm QJ- edelbrock 110 gph mech fuel pump- 4 row copper rad- followed by a Th400 w/2300rpm stall then a nodular 10 bolt posi w 3:90 gears ( need 3:55 bad
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Old 12-28-2016, 11:26 PM
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The 462 will like the 3.36 gear.

I ran a 3.25 gear and 28" tires behind a std. bore 455 for a while.

It didn't suck.

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Old 12-28-2016, 11:29 PM
mtnbktrek mtnbktrek is offline
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thats what im thinking too

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1968 LeMans Convertible - 462 w hydo roller comp cam forged flat tops- 6x-4 heads- performer intake - 800 cfm QJ- edelbrock 110 gph mech fuel pump- 4 row copper rad- followed by a Th400 w/2300rpm stall then a nodular 10 bolt posi w 3:90 gears ( need 3:55 bad
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Old 12-28-2016, 11:46 PM
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Good friend with a similar build just swapped from 3.55 to 3.08 and is very happy with it. Couldn't really drive on street with the 3.55s. He does have ported E-heads though.

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Old 12-29-2016, 12:14 AM
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With the 462 I would go 3.08.I have 3.36s in my bird with a OD 5 speed.If I had a 4 speed it would be 3.08.Tom

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Old 12-29-2016, 12:56 AM
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TH400 is great at multiplying torque to rear wheels. When bracket racing a 70 Corvette 454/TH400 it really ran very well with 3.,08. I tried many rear ends, 4.11 (sucked) 3.70 (almost as bad as 4.11) 3.55(much better but still a bit steep) 3.36 (very good) 3.08 (liked 3.36 better but ran just as quick)
The car would et just as well with 3.08 as the steeper ratio's. We figured the very good torque multiplication of the mild stall converter (about 3000) compensated for any gear reduction. Just a street car, 12.80's at 106mph thru the mufflers.
With a big torque motor and a TH400 I would do 3.36 or 3.08 if it's primarily a street car.

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Old 12-29-2016, 01:02 AM
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I have a 3.42 gear with a 455/KRE/HR engine and a 200-4R (2.74 1st gear) trans and 1st gear is basically useless (26.4" tire).

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Old 12-29-2016, 02:34 AM
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Over the last 15 years I've had a stockish 455 4 speed 3.23 geared 76 Trans Am,a 1980 Trans Am that started as a 375hp 455 308 gears stock convertor,then 3200 convertor,then 3.42 gears.A couple years later hyd cam and new alum heads 500hp plus.Fast forward to current car 550hp plus 3.08 gears and 3200 convertor.The 3.08 gears are the most highway friendly you can cruise fast and for long distances..the 3.23's were a nice gear in the 4 speed car still pretty good on the highway.The 3.42's were still ok on the highway but the rpms are up about 250 rpm.The big torque output of a 455 doesn't really need much gear to perform well.

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Old 12-29-2016, 04:47 AM
mtnbktrek mtnbktrek is offline
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Ok thx all I'm going to go with the 3.36's.
Thx

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1968 LeMans Convertible - 462 w hydo roller comp cam forged flat tops- 6x-4 heads- performer intake - 800 cfm QJ- edelbrock 110 gph mech fuel pump- 4 row copper rad- followed by a Th400 w/2300rpm stall then a nodular 10 bolt posi w 3:90 gears ( need 3:55 bad
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Old 12-29-2016, 06:30 AM
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FWIW - I just pulled the 3.42's out of my '64 GTO and replaced with 3.08's and am very happy.

This is with a 9.5 compression 462 with a Crower 60243, #96 heads and an 800 CFM Quad and a 4spd with 27" rear tires.

I expect you'll still have a smile on your face with the 3.36's.

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Old 12-29-2016, 07:09 AM
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If you do not run drag radials and 75% or more of your driving is on the street, then the 3.36 is the way to go.

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Old 12-29-2016, 08:15 AM
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I've ran 2.73, 3.23, 3.42's and 3.73's behind several engines in my Ventura.

With the 455 the best overall is the 3.42's teamed up with 28" tall rear tires.

Of course the torque converter is a BIG player with these things, and I have one of the very best converters ever made for one of these engines in place.

For freeway driving speeds you'll still find rpm's pretty high with anything much past 3.08's, but 3.42's with 28" tall tires provide acceptable rpms even at 65-70mph.

Here is the formula I use to compute engine RPM's at any given vehicle speed:

MPH x GEAR RATIO x 336 divided by TIRE DIAMETER.

If you have OD multiply the end result by the OD ratio to compute RPM's as that formula is for a 1 to 1 high gear ratio.......Cliff

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Old 12-29-2016, 09:30 AM
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I've ran 4.10, 3.90, 3.54, 3.42, 3.31, 3.23, 2.73, and 2.54

The 3.31 was fine with a high compression 469 on the highway, 1/4, and street.
The 3.23 was unnoticible with a 350.
The 2.73 was loads of fun with a hi compr 455.
The 2.54 was loads of fun with a hi compr 400, too bad it had a manual (3-speed was load of fun except for stoplights.

Presently at 3.54 with a low compr 469, NOT fun with too much highway rev. Would be better with a stick, an OD, or high compr.

Strong opinion here for 2.54 thru 3.31 for a bored out 455. Any higher is less fun with an automatic.

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Old 12-29-2016, 10:59 AM
Steve C. Steve C. is offline
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And when calculating rpm/s don't forget converter slippage if automatic.


.

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Old 12-29-2016, 01:03 PM
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i miss my 3.36 i have 3:42 now 26" tire with a th350 10" converter thinking of going 3:08 or 200R4

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Old 12-29-2016, 01:46 PM
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Like most here, I've run everything from 2.73's up through 4.88's on the street. None of them had or have overdrives. We currently have one of our daily drivers with 3.55's and a 27" tire, and I find it cruises just fine. Nice compromise between streetability and a little track time.
I've done cross country trips with 3.73's (no overdrive) and really don't have a problem with it. I figure if I can cruise at 65-70 mph at 2800 rpm or so, I'm good with that.

However if I were building something like a 455 with a lot of grunt down low, and had more street driving in mind, I'd probably look at something between 3.23-ish to 3.50-ish, probably run a 28" tire on it if it fits, Then just drive it and not worry about it. When you want some track time run a dedicated pair of 26" sticky tires.

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Old 12-30-2016, 07:44 AM
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Quote:
Originally Posted by Formulajones View Post
Like most here, I've run everything from 2.73's up through 4.88's on the street. None of them had or have overdrives. We currently have one of our daily drivers with 3.55's and a 27" tire, and I find it cruises just fine. Nice compromise between streetability and a little track time.
I've done cross country trips with 3.73's (no overdrive) and really don't have a problem with it. I figure if I can cruise at 65-70 mph at 2800 rpm or so, I'm good with that.
27" tire, 3.73's and no overdrive at 2800 RPM is only 60 MPH. 70 MPH would be 3250.

I have 27.1" rear tires on my GTO and I just switched from 3.42's with my 462 to 3.08's to drop my RPM's from nearly 3000 at 70 to under 2700 so I knew the numbers...

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Old 12-30-2016, 09:55 AM
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Sorry, should have been more clear. The car I have done cross country trips in with 3.73's has 28" tires, and 65 is exactly 2800 rpms.

My daily driver has 3.55's with a 27" tire, and it goes 65 at 2900 rpms.

Either car will go 70 mph easily enough if I push another 200 rpm or so. To me not that big of a deal. I've done 2,000 mile road trips like that.

What I was trying to convey, no matter what the mix of tire height or gear ratio, as long as I can cruise 65 mph somewhere in the range of 2800 rpm, I'm good with that. And I usually knock down pretty decent mileage doing it. So I'll adjust the gear and tire height accordingly to accomplish that goal. Any time I can fit a 28" rear tire on a particular car, I'll run it that way. Cruising like this makes a nice driver for us and just hasn't really been a big deal to me. Been driving them for decades like that.

Even with that said, I do like the idea of a big grunt engine running a very high gear ratio. 3.08's would be fine like that, especially if you had to run a shorter tire.


Last edited by Formulajones; 12-30-2016 at 10:07 AM.
  #19  
Old 12-30-2016, 07:31 PM
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You sound like you travel like me to get anywhere, I run 3.36 and they give me enough grunt with my 400 auto.

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Old 12-30-2016, 08:31 PM
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Default 3.36 for a driver

If it's a driver, I'd vote for 3.36 over 3.55 all day long.

My Goat has 3.55s with 26" tires and a 700R4 behind a mild 389. 1st gear is a granny gear and drives me NUTS stop light to stop light. I'm gonna switch to 3.23s when I save the money. With taller tires (27 to 28"), I'd think 3.36 is perfect for all around fun.

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