Another Rear End Set Up Question/Advise

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73Vert302

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RE: transmission and rear end question

Hey everyone, I was looking for some advise on my new set up I have planned for my 73. The new motor is at the machine shop and will be a 466ci with 550 hp and

545ft/lbs of torque at 4800 rpm.

I found a 9" rear end that is about 3/4" shorter width than my stock 8" rear. I assume the 3/8" (each side) difference wont matter and allow me to tuck some wider/bigger tires underneath. The Third Member has 2.69 gears. Looks like it will be a smooth ride on the highway, but allow me to light em up from a stop if I feel like it. Problem is the gears are open and not posi. I am spending so much on the motor...I need to keep the costs down a little on the drivetrain.

ANY info will help...thanks in advance. I look forward to hearing from you!

 
RE: transmission and rear end question

Hey everyone, I was looking for some advise on my new set up I have planned for my 73. The new motor is at the machine shop and will be a 466ci with 550 hp and

545ft/lbs of torque at 4800 rpm.

I found a 9" rear end that is about 3/4" shorter width than my stock 8" rear. I assume the 3/8" (each side) difference wont matter and allow me to tuck some wider/bigger tires underneath. The Third Member has 2.69 gears. Looks like it will be a smooth ride on the highway, but allow me to light em up from a stop if I feel like it. Problem is the gears are open and not posi. I am spending so much on the motor...I need to keep the costs down a little on the drivetrain.

ANY info will help...thanks in advance. I look forward to hearing from you!
Click to expand...
So what is your question? If you want cheap posi, there ain't no such a thing.

 
I wanted opinions on the setup. I will run with the open spool until I get a posi. But I wanted to see if anyone had problems with the axle width or any opinions on a better set up for city and freeway driving with this motor based on experience.

 
I wouldn't be too concerned about the width, the difference can be made up in the wheel backspacing or spacers.

However, 2.69 will likely be too high of a ratio for your torque curve. That ratio is more suitable for a stock engine that develops maximum torque around 2,500 rpm for both moving off the line and for cruising down the highway. I would be looking for something in the 3.50 to 3.73 range, or lower.

 
I wouldn't be too concerned about the width, the difference can be made up in the wheel backspacing or spacers.

However, 2.69 will likely be too high of a ratio for your torque curve. That ratio is more suitable for a stock engine that develops maximum torque around 2,500 rpm for both moving off the line and for cruising down the highway. I would be looking for something in the 3.50 to 3.73 range, or lower.
Click to expand...
Thanks Don! I will see if I can find a Third Member-Posi in that range. What will the car do with 2.69 gear ratio? Still trying to get a handle on the gears and how it relates to the performance.

 
It's going to be slow off the line if that what you're asking. It will turn 2435 RPM at 70MPH with 26" diameter wheels assuming 1:1 final tranny drive ratio. Not even close to your torque band.

 
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What s 2.69 will do is keep your engine in a low rpm range on the highway but it will have to work harder to accelerate. A higher number on the rear end (like 3.55) will make it easier for the engine to accelerate the car but it will rev higher at the same given speed.

Is that what you meant to ask?

 
What s 2.69 will do is keep your engine in a low rpm range on the highway but it will have to work harder to accelerate. A higher number on the rear end (like 3.55) will make it easier for the engine to accelerate the car but it will rev higher at the same given speed.

Is that what you meant to ask?
Click to expand...
+1

I would think a 3.50 or 3.70. I would probably do around 3.50 as Mike has mentioned. You would be turning around 3000 rpm at 70mph but you will notice a real big difference off the line.

 
What s 2.69 will do is keep your engine in a low rpm range on the highway but it will have to work harder to accelerate. A higher number on the rear end (like 3.55) will make it easier for the engine to accelerate the car but it will rev higher at the same given speed.

Is that what you meant to ask?
Click to expand...
Yes, thanks. I really appreciate all the feedback. It helps a lot!

 
Heck I would give that 2.69 a shot. You have gobs of torque. You're going to be spinning tires regardless.

What motor/cam/comp ratio are we looking at? What are you using for a transmission?

 
My car came with a 3.25 and was replaced with a 2.75 years before I bought it.

At 70 you are turning around 2200. The car will accelerate smoothly starting in

2nd gear, not sure I need a 1st gear. Car has a wide ratio toploader. The engine

is a mostly stock (some kind of cam) 351 Cleveland D0AE.

I have a 3.50 waiting to be installed that I purchased from Don Witt at Ohio Mustang Supply,

a site vender. Don't look on his site rather PM him. The one I got from Don is Trac-Lok for

a good price and looks brand new.

HPIM3199.JPG

mike

 
Heck I would give that 2.69 a shot. You have gobs of torque. You're going to be spinning tires regardless.

What motor/cam/comp ratio are we looking at? What are you using for a transmission?
Click to expand...

466, not 100% sure about the cam, 10-1 Compression

And C6 Tranny

 
Last edited by a moderator:
Not doubting, but those are fairly juicy numbers for a 10:1 / 466incher.

Are those actual dyno'd numbers?

The cam will make a HUGE difference as to where and when the power is delivered, along with the heads (iron/aluminum/CJ/SCJ, etc) and intake manifold.

That knowledge will help immensely with rear gear and trans/converter choice.

It all works as a package.

 
I always find 3.25 a good all round ratio.
Click to expand...
yup . . this is your number plus you will likely need around a 2000 rpm stall converter.

 
So we need more info on the engine. Ford didn't make a 466 so what was it originally and how did we get to 466? These things are always a combo package. Do you know what the stall converter is on your C6? And what kind of driving will you do? Freeway cruising? Night at the drag strip? All around daily driver?

 
The 460 is bored .030 over which equates to a 466, right? Trick Flo aluminum heads, Edelbrock Air Gap intake, Q850 carb. Its still at the builder. Working on the drivetrain...or at least getting ready. Found a 3.25 Traction Loc for $200.00 today. Is that a fair deal?

Want a fun driver in the city and a comfortable (as possible) for a highway drive.

 
Last edited by a moderator:
The 460 is bored .030 over which equates to a 466, right? Trick Flo aluminum heads, Edelbrock Air Gap intake, Q850 carb. Its still at the builder. Working on the drivetrain...or at least getting ready. Found a 3.25 Traction Loc for $200.00 today. Is that a fair deal?

Want a fun driver in the city and a comfortable (as possible) for a highway drive.
Click to expand...
I believe it would be 474

 
Last edited by a moderator:

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