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Gear Set Question



 
 
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  #1  
Old May 20th 05, 06:03 AM
SharkMan
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Default Gear Set Question

Hello,

I have a Mustang with a 347 putting out 475hp. I plan on road racing
this car, no drag racing ever. I am a driver, not a mechanic, so I
looking for a second opinion. The shop doing the work on the car wants
to put in a 3.73 gearing. I was thinking 3.27 would be better for
economy and top end performance. I was hoping someone out there could
help me with this.

Thanks!

David

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  #2  
Old May 20th 05, 06:20 AM
.boB
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SharkMan wrote:
> Hello,
>
> I have a Mustang with a 347 putting out 475hp. I plan on road racing
> this car, no drag racing ever. I am a driver, not a mechanic, so I
> looking for a second opinion. The shop doing the work on the car wants
> to put in a 3.73 gearing. I was thinking 3.27 would be better for
> economy and top end performance. I was hoping someone out there could
> help me with this.
>
> Thanks!
>
> David
>

There is no one perfect gear for all road courses.
That's why professional race teams carry multiple
gear sets to the track.
If you're only racing at one track, it's a lot
easier. What is the top speed you'll expect to attain?
Try and select the gear that places you just past the
peak of the torque curve at that speed in 4th (1:1) gear.
That will be a good place to start. But expect to
make a change or two as the season progresses.
Optimally, you'd want a 8 inch rear, with multiple
center sections. The center section can be swapped out
in less than an hour the first time. All it takes is a
couple of hand tools. Even a non-mechanic can do it.
The 8.8 is plenty strong enough, but since it has
an integral carrier changing gears is time consuming
and requires special skills and tools. A 9" rear is
stronger, but also requires more power to run it. A
well built 8" will last forever on a road course, will
be lighter, and will deliver a little more HP to the
ground.

--
..boB
1997 HD FXDWG - Turbocharged!
2001 Dodge Dakota QC 5.9/4x4/3.92
1966 Mustang Coupe - Daily Driver
1966 FFR Cobra - Ongoing project

  #3  
Old May 20th 05, 09:02 AM
Jim Warman
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Default

Kinda following up on what boB says..... (and I hope you mean a race track
when you say "road racing")..... there is no finite answer toyour question.
30 years ago, we would have said the best gear ratio is the one that has you
at max RPM in high gear (direct drive at that time) just before you have to
apply brake at the end of the longest straight. With the equipment that is
available now, and the money willing to be spent, the equation has grown to
many, many more steps than what we have been use to.

The ideal situation has us being able to keep our RPM in the area where our
peak torque is being developed in acceleration conditions and where peak HP
is being developed during sustained high speed conditions. The ideal
situation also has us in "direct"... that gear that gives us a 1:1 ratio to
avoid gea losses.

The question you have offered is difficult to answer.... add the query
regarding 'economy' and all bets are off.

Decide on your priorities and then ask te question again stating what you
expect *within reason*. .....


"SharkMan" > wrote in message
oups.com...
> Hello,
>
> I have a Mustang with a 347 putting out 475hp. I plan on road racing
> this car, no drag racing ever. I am a driver, not a mechanic, so I
> looking for a second opinion. The shop doing the work on the car wants
> to put in a 3.73 gearing. I was thinking 3.27 would be better for
> economy and top end performance. I was hoping someone out there could
> help me with this.
>
> Thanks!
>
> David
>



  #4  
Old May 20th 05, 11:12 AM
RSCamaro
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Default

On 19 May 2005 22:03:11 -0700, "SharkMan" >
wrote:

>Hello,
>
>I have a Mustang with a 347 putting out 475hp. I plan on road racing
>this car, no drag racing ever. I am a driver, not a mechanic, so I
>looking for a second opinion. The shop doing the work on the car wants
>to put in a 3.73 gearing. I was thinking 3.27 would be better for
>economy and top end performance. I was hoping someone out there could
>help me with this.
>
>Thanks!
>
>David


The short answer I think is that you'll want more gear once you get
out onto the track. In my 00' GT the 3.27:1's are ok but in lower
gears take more time to come back up to torque peak. I have 3.42's in
another car with much less power and coming out of the corners I get a
better pick up than with the Mustang. Both have the BW T-5
transmission.

...Ron
--
68' Camaro RS
88' Firebird Formula
00' Mustang GT Vert
  #5  
Old May 20th 05, 02:20 PM
SharkMan
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Default

Hi Bob,

Sorry, I guess more information is neeed. So here it is.

Rear End - 8.8, all 31 spline with Auburn Pro
Transmission - the new TKO-600
TCET4617 Ford 1st - 2.87 2nd - 1.89 3rd - 1.28 4th - 1.00 5th - 0.82
rev - 2.56

The road racing I am taking about is not just track based, but also
open road racing like the Nevada Silver Stakes Race. My car is speed
classed to 160 mph. It can go faster once I do more aerodynamic work.

Thanks for the advice on the center section, I will look into that. It
is my desire not to be helpless with a wrench in my hand.

Thanks for the information.

Respectfully,

David
1983 GT Hatchback

  #6  
Old May 20th 05, 02:37 PM
SharkMan
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Default

Hello Jim,

Please see my response to boB. I think most of your questions are
answered there. By economy, I am saying that with tight gas
allocation, I need gearing that will be able to make the tank last the
length of the race.

I am not a street racer. I will be running only in SCCA sanctioned
events. I mis-typed in my previous response, it is the Nevada Silver
State Classic. These are the types of races I will be running. The
distances vary between 90 to 125 miles. So I am looknig for the
gearing that will make the 22 gal fuel cell last to the finish line.
The last thing I want to do is not finish by running out of gas. I am
not sure what the fuel consumption will be just yet. The dry empty
weight of the car is around 2400 pounds. I also will have a race-built
331 available shortly meaning Race gas only. The 347 is all SFI
approved, but the engine will run on 92 octane gasas an emergency
back-up car. I.E. when my daily driver is in the shop.

I hope this makes a litle more sense now.

Thanks for your advice,

David

  #7  
Old May 21st 05, 11:19 PM
Jim Warman
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Default

OK... I was thinking strictly in terms of close course racing. The 3.73s
would be a pretty drastic change and may reduce your top speed. There are
several free gear ratio calculators on the internet that will let you
compute theoretical top speeds for different ratios. These may help make a
decision for you.

If you follow boBs advice and go with a banjo style housing (and your racing
budget will allow it), changing ratios for sifferent tracks/events can go
pretty quick if you only need to swap out the pumpkin.



  #8  
Old May 22nd 05, 06:49 AM
mustrang888_8@ yahoo.com
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Default

On Sat, 21 May 2005 22:19:32 GMT, "Jim Warman"
> wrote:

>OK... I was thinking strictly in terms of close course racing. The 3.73s
>would be a pretty drastic change and may reduce your top speed. There are
>several free gear ratio calculators on the internet that will let you
>compute theoretical top speeds for different ratios. These may help make a
>decision for you.
>
>If you follow boBs advice and go with a banjo style housing (and your racing
>budget will allow it), changing ratios for sifferent tracks/events can go
>pretty quick if you only need to swap out the pumpkin.
>
>

lmfao
jim your my pumpkin


h
u


r
c



a

s
t

  #9  
Old May 23rd 05, 04:52 AM
SharkMan
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Default

You ilterate moron, keep your stupidity to yourself. Go play with your
16 cats and stop trying to act like you know anything!

 




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