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Old 02-26-2004, 02:38 PM
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what rear gears for the best launch?

Hey guys,
I am currently in the process of building up my '78 T/A into a nice street machine. I will be using a 455 that is .030 over and pushing roughly 460 horses and 550ft/lbs torque. The tranny is a richmond 6-speed with 3.27 first gear. The current gears in the car are 3.08's. This is not going to be a strip car but maybe the occasional trip down the drags. Mostly it will be a cruiser. I can't remember the tire size it has on it, but I know they are a little wider than stock.

My question is what would be the better ratio gears to use to get the best hook up and least wheel spin (if possible)? 3.23, 3.42, 3.55 or just stay with the gears I have?

Thanks for any input guys, I appreciate it

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Old 02-26-2004, 04:23 PM
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Re: what rear gears for the best launch?

Quote:
Originally posted by BanditT/A

My question is what would be the better ratio gears to use to get the best hook up and least wheel spin (if possible)? 3.23, 3.42, 3.55 or just stay with the gears I have?

From the selection you listed the 3.55 gears would be best for what you want.

Actually, I'd suggest 4.11 for the street with your combo and 4.56 for the strip.

The tire DIAMETER is important when figuring the correct rear gearing.
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Old 02-26-2004, 05:42 PM
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Well this is just my opinion. I wouldn't go too crazy on the gears if it was mine and a mostly street car. That 3.27 is a pretty low first gear. The average automatics first gear is around 2.50. What your final gear ratio is will also play a role as well as tire diameter like Frisco said. This is just a guess but I would think with a torquey (is that a word?) engine and a pretty low first gear you will not need too much gearing. Since the 3.08's are already there I would run them first to establish your RPM's for different gears and then decide how much of an increase you want. Just my 2 pennies.

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Old 02-26-2004, 06:14 PM
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Thanks for the replies guys!
I was thinking of using the 3.55 ratio but not really sure.

Dmorris, good point of just trying the 3.08's I have now. I am just trying to see if anyone else has experience with this.

Im not real sure on tire diameter, I think they are around 26 inches tall. The sixth gear is .76:1. I have heard that running a lower gear (ie. 4.11's) with street tires and a high torque motor will cause major traction issues. But a higher rear gear (say 3.23's) and high torque motor will spin the tires slower so it will have better traction. But this is what I have heard. Has anyone else heard this?
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Old 02-26-2004, 06:38 PM
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The beauty of a torque monster like a 455 is you can run relatively mild gears without losing so much.
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Old 02-27-2004, 12:56 AM
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Stick with the 3.08's for now.
What you have heard is correct.
4.10s or 4.11s come stock on alot of 4cyl auto vehicles because they need the torque to take off, and dont produce enough to spin the tires.

If you went with 4.11s with your 455 you will need big fat tall tires, and need to start off in 2nd gear at the track to keep from spinning the tires.

4.11's are a good gear with a 2spd powerglide, whose first gear is probably close to your 3rd.

You will probably need better tires even with the 3.08's to keep from spinning out in first gear. I recommend starting with some 255/60/15s. If you can't spin them, up your rear to a 3.23 and experience tells me you will (even with a th350). A 455 is a lot of engine.
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Old 02-27-2004, 10:17 AM
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I think you guys have a good idea in just sticking with the 3.08's. But the only thing is it's a single digger, not posi. And I'm thinking the motor will most likely cause the gears to blow out the cover. So I will probably end up changing them sooner or later.
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Old 02-27-2004, 08:42 PM
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Actually since its an open rear you'll be putting less stress on the rears internals because your only directing power to one wheel. The 8.5inch 10 bolt thats in you bird can be built to handle that monster torque from the 455. You can run it like it is for a while, and just have some fun with it. You will have to plan to eventually get some stronger axles, a posi unit (Eaton makes a good one), and a new ring and pinion (any quality brand such as Richmond).

I'm also going to say maybe consider a C clip eliminator kit. DO you guys agree?

Mike
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Old 02-29-2004, 05:55 AM
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If he plans to track it a bit, then he will need bulletproofing. Especially if he finds a way to keep traction with a lower gear. The 8.5 came stock with all the 455s, but if you can get the power to the pavement with anything lower than a 3.08, you may want to consider the ford 9". If you keep spinning tires, the 8.5 will hold just about forever.

So yes. I agree.
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Old 03-01-2004, 02:52 PM
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Ghetto

I would save the money and put it in to the Eaton. Distribute that torque across both axles. With that six speed gears and then boosting the rear to 4.XX you are way over the axles ability. Good car, good motor, good trans, BAD axles. Eaton first, then maybe up to 3:42. You do not want to feel that axle go as you hit 3rd, believe me.

hr41pearl
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