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Old 06-04-2013, 11:03 PM
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57 Chevy Belair gear ratio selection

hello guys!
im almost done buying parts for my 57 Chevy belair.
ive done a cal tec tubular front suspension
roller 383 designed to put out 460 to the fly.
t-56 magnum with a 0.50:1 final drive.
currie 9" and a complete 4 wheel disc brake.
i have not bought the center section yet.

anyone wanna help me out? on their gear ratio, and speed on the freeway @ 2,000 rpms in 6th???
greatly appreciated!

i will be running aprox. 28" tall tires.


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Old 06-04-2013, 11:21 PM
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Using your data I found 2 ratio's that would be close based at 70 mph....... 3.70 = 1926 rpm, 3.89 = 2025 rpm. Before you buy a gear set make sure your engine will be happy running at 2,000, don't want to lug it.
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Old 06-04-2013, 11:37 PM
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Thank you! it most likely wont see much time at that exact RPM.
i just threw that number out there to get an idea.
i want to beable to cruise on the freeway comfortablly.
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Old 06-04-2013, 11:49 PM
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Quote:
Originally Posted by h0trod View Post
Thank you! it most likely wont see much time at that exact RPM.
i just threw that number out there to get an idea.
i want to beable to cruise on the freeway comfortablly.
Here are a number of gear/RPM calculators.
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Old 06-05-2013, 06:31 AM
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With the .5 overdrive, 28 inch tire and a 4.88 gear you will be at 2050 at 70 MPH. You are going to need a really good drive shaft for this.
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Old 06-05-2013, 07:14 AM
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Make sure you balance your rear gear with the 1st gear as well. Multiply the rear gear times the 1st gear.
For example: lets say you had a 69 Camaro with 4.11s and a Muncie Rockcrusher for a baseline. Take the 4.11:1 rear gear x 2.20:1 first gear = 9.04:1. That's a good benchmark for a performance oriented 'Starting Line Ratio' or 'Total Mechanical Advantage'. Anything from 9-10:1 is useable comfortably on the street. If using an aluminum flywheel, you may way to hedge closer to the 10:1 mark or more.

Do you have the 'close ratio' or wide ratio TR6060 (sold as the "T56 Magnum")?
Close ratio would be the 2.66 1st gear, and the wide is (I think) 2.97. If you have the CLOSE, I would run at LEAST a 3.73; up to say a 4.56. If you have the WIDE, run something like a 3.73. What you don't want is a first gear thats too deep to be practical. Guys who miss these kinds of things end up with a 6speed that becomes a really big 5 speed because they either dont have enough rear gear to make 6th useable often, or a tractor like 1st gear thats useless and they usually start off in 2nd. A lot of this depends on your driving style.

Contact your engine builder or cam manufacturer and find the cruising RPM for your combo; target for that, ESPECIALLY if carbureted.

Footnote: as I mentioned earlier, the 'T56 magnum' is NOT a T56; it is the current generation 6 speed (called the TR6060) produced by Tremec and sold by their North American counterpart as a crate transmission. Write down the Tag Number on the gearbox (something like TUET7744 or TUET11009) as this is the only way to get parts and service for one should you need it. If you don't know what ratio's you have, post the tag number and I'll gladly look it up for you.
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Old 06-05-2013, 08:43 AM
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T56 ratio chart

Borg-Warner T-56 transmission - Wikipedia, the free encyclopedia

Nice '57 , Here's a chart for you. As you've already been advised, pay attention to your total first gear ratio and have a custom driveshaft built to deal with the high driveshaft speed.

My setup with a 2.66 first and a 4.10 rear creates a 10.91 total first gear ratio. It's a stump pulling first, but forces you to have to pull 2nd while you're still trying to control the car from the 1st gear launch at the track. It also forces you to have to shift 2nd in the middle of a turn at red lights and stop signs, which I find aggravating. I feel that a 3.73 rear would likely be better (2.66x3.73=9.92), but i'm just living with whats there(ain't broke, don't fix)

Example on the driveshaft, my wifes Z28 has the puny stock drive shaft and you can feel the driveshaft start to vibrate at about 80-85 mph in overdrive with a 3.23 rear. It gets worse at speeds over 100mph. My SS has a custom built 3.5" aluminum driveshaft, no vibration at all, at speeds all the way on the right hand side of the speedometer. Nolan
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Old 06-05-2013, 09:17 AM
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Nolan;

Is that the factory 4th Gen aluminum D/S?
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Old 06-05-2013, 09:20 AM
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first gear = 2.97:1
with a 3.75 reargear that im leaning towards,
gives me a 1st gear ratio of 11.13.
second is a 2.1:1
3rd is a 1.46
4th is a 1:1
5th is a .74:1
and the final is .5:1

according to the other magnum with a final drive of .63:1
i have the close ratio

with a billet steel flywheel

i may want to get a taller gear..
what do you guys think?

and yes a aluminum driveshaft is a must. i dropped some serious coin on this car, and im not going to be a cheap a*$ on anything on this car.

i appreciate all of your guys's help!
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Old 06-05-2013, 09:48 AM
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Just to clarify; 2.97 is the WIDE ratio. 2.66 is the close ratio.
*to put this in historical perspective; the 2.52 wide ratio M20; and the 2.64 & 2.43 1st gear T10s are all closer ratio compared to todays 'close ratio' gearboxes*

Id say you're on the right track with your build, given the parameters. Make sure if you get an aluminum driveshaft, A. its spin balanced for the RPMs you're planning on, and B. the tube size and wall thickness are sized properly for your application. You may want to consider a bolt in driveshaft loop as a measure of safety and perhaps a set of 1350-series U-joints

Disclaimer: The following comments aren't meant as a reflection of your build, but rather to point out some areas that other builders may not know they need to take into consideration

You're kind of in a bit of a compromise. In reality; you could put 3.08s in the rear and not even use the OD at all, with that 2.97 1st gear (9.14:1 Starting Line Ratio). Being a carbed car, we need to remember that we can't drop the RPMs too low at cruise, as driveability and mileage will suffer. But, the flip side is: you have a TON of first gear and a stump puller of a motor.

Gorgeous 57 Chevy; and Im sure you're going to enjoy the hell out of it.
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Old 06-05-2013, 02:20 PM
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Driveshaft

Quote:
Originally Posted by AutoGear View Post
Nolan;

Is that the factory 4th Gen aluminum D/S?
Nate, My wifes '94 Z28 is bone stock. We ordered it new, LT1,4L60E,3.23 limited slip. 4L60E od is .7:1 Its a small steel driveshaft. When all the new was worn off, I went to top end run it(its supposed to do 150) and noticed the vibration frequency starts above 80-85 and increases with speed. The cure is a 1LE option aluminum driveshaft. I told my wife how it would be a good idea to get the 1LE piece, she said, just keep it under 85, its MY car. I could have ordered it with the 1LE package, but the factory warns you in big print that the ride is extremely harsh and should be only used in racing applications and police pursuit vehicles. She said no on the 1LE and I want T-tops, it is HER car. Oh, It will do a buck-fifty

My '97 SS has a PST 3 1/2" custom built shaft with 1350 u-joint setup, T56/2.66 1st, Moser 12 bolt, 33 spline axles,4.10 posi. It has no vibration at all. Haven't ever tryed to top end this one, ain't a safe enough road around here and besides, I don't wanna go to jail.
Maybe some day, Ohio Mile or Nevada Speed Challenge. In the meanwhile just the dragstrip.

Sorry about the hi-jack h0trod. Nolan

Last edited by OLNOLAN; 06-05-2013 at 02:25 PM.
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Old 06-05-2013, 02:27 PM
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Along w/a strong, correctly balanced driveshaft with good U-joints, be sure the driveline angles are optimized as best as they can be due to the high driveshaft RPM seen w/that low final drive ratio.
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Old 06-05-2013, 02:56 PM
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Try this again

h0trod, I was trying to post but my computer kept trying to lock up. Ok, if you've got the 2.97 1st, a 3.42 would likely be a good gear IMHO. 3.42=10.16 in 1st. 3.73=11.08 in first which would be just like my 2.66 w/4.10's.

Now keep in mind what 327NUT said about lugging. If this 450-460hp stroker has a pretty big cam, it ain't gonna be happy in 6th gear at low speeds(its gonna lug the engine). Might not be able to shift to 5th or 6th until you're exceeding the speed limit by alot. The rear gear selection may be a trade off between enough to make the od gears useable at highway speed and not so low as to make first gear like a tractor. Alot of the rear gear selection process also involves how much camshaft is in the engine when it comes to double overdrive transmissions. My big X large camshaft tries to lug the engine at anything under 3000. Food for thought. Nolan
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Old 06-12-2013, 01:43 PM
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Gear Ratio chart

Go to this web site on the Tri Five site and it lets you select tire size, transmission type different ratios and you can see the RPM at any given speeds etc.

Gear Ratio Calculator
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