what rear gear to choose for road racing

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Duster708

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gota 489 8 3/4, mid 70's 4 speed, wondering what gear to choose for road racing and auto crossing
 
Road racing and autox are two different things. My guess is you will be looking at having several 3rd members set up and ready to run, depending on which event you are doing.
 
If you're doing the silver state run (top speed stuff) you'll want 2.94 or 2.76. If you're doing a track event then 3.73 or 3.91 to get you car up and moving (not a lot of chances to run at top speed, think of it more as stop light to stop light, it's all about the get up and go).
 
We run a 3.73 in a road racing mustang but it does have a 5 speed. I would say depending on tire size and trans you would probably want a gear in the 3.55 to 3.73 range
 
Depends on the the track, rear tire dia, and motor (whats your powerband look like).

Close ratio trans is optimal. Tremec's are not optimal. But still good dual purpose trans and still better than automatic.

A detroit locker or true track (torsen gleason) are the best.
 
autoxcuda said:
A detroit locker or true track (torsen gleason) are the best.
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Really? I'm not trying to argue.....Lord knows you got the experience here, but would you expound on this? My stupid brain tells me a locker would try to push through turns. What would make it better for road racing? I know all the dirt boys down here use open diffs. That might not be a good comparison, though. Learn me sumffin. lol
 
cars under construction tryn to get the pieces n i thought about haven a couple pigs set up with different ratios, but engines a 440 (not rebuilt yet) expecting round 500 horse minimum, and im gona put a tru trac in the rear..
i cant work on it everyday bc got college courses n work during the week so things get done in spurts. just looken for some input. thinkn bout builden it for 150mph range
 
also gota budget goen n i just bout the hotchkiss tvs kit my goal for this year was to get it in a roller chasis atleast
 
StrokerScamp said:
Really? I'm not trying to argue.....Lord knows you got the experience here, but would you expound on this? My stupid brain tells me a locker would try to push through turns. What would make it better for road racing? I know all the dirt boys down here use open diffs. That might not be a good comparison, though. Learn me sumffin. lol
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Paved oval track most all run Lockers or Torsen if rules allow. Most only allow Lockers for cost reason. Some classes only allow spools for cost reasons. And I don't think there's a big advantage on a Torsen for a circle track car and they add weight.

You have to drive a Locker a little different. Got to be a little more deliberate off and on throttle. Car is just setup a little different (f/r balance) to compensate. Back in the day Trans Am cars ran lockers.

Torsen seems to be a better autocross and street diff. Autocross is very tight and those racers seem to prefer Torsens. There are people that run Lockers in autocross, but Torsens seem most popular.
 
autoxcuda said:
Depends on the the track, rear tire dia, and motor (whats your powerband look like).

Close ratio trans is optimal. Tremec's are not optimal. But still good dual purpose trans and still better than automatic.

A detroit locker or true track (torsen gleason) are the best.
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Regular TKO i agree. My liberty gears synchroed TKO shifts better than any car i have ever felt. Just my 2 cents. Maybe its comparing Apples to Green apples.

But what is the down fall of our factory style cone/clutch sure-grip on the track/course ?
 
With his specs and requirements, he'll need something stronger than a factory 8 3/4.
 
the difference in wait isnt really that much and thats what i got for right now if some deal for a small block falls outa the sky then i might buy it
 
Lakeeffect said:
Regular TKO i agree. My liberty gears synchroed TKO shifts better than any car i have ever felt. Just my 2 cents. Maybe its comparing Apples to Green apples.

...
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It's not the good vs. bad shifting. It's the gear spacing/spread that's too far apart from optimal for most road course.

But what is the down fall of our factory style cone/clutch sure-grip on the track/course ?
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Slippage, heat buildup, etc. We're talking sticky race tires that grip the pavement and don't slip like street tires. The less the tires slip, the more the wearable cones/clutches have to slip.
 
Duster708 said:
gota 489 8 3/4, mid 70's 4 speed, wondering what gear to choose for road racing and auto crossing
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There is no answer for you with that. . .


What is the cars weight...

What is the hp you make, what is the RPM band you want to remain in

What are the tracks you expect to frequent. . .

auto x. . .might want 4.56 . . .

You will nee to go buy a few more 489's, and still need some motor info.. a 2.90 may never ever fit any use other than bonneville, you may need a 3.90 as your shortest, you may need several centers, 3.90, 4.30, 4.56. . .and more
 
Supershafts said:
You will nee to go buy a few more 489's, and still need some motor info.. a 2.90 may never ever fit any use other than bonneville, you may need a 3.90 as your shortest, you may need several centers, 3.90, 4.30, 4.56. . .and more
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if he's aiming for the 150 mph range, seems to me the 2.90 (or thereabout) is pretty much the only option, unless that big block is gonna turn some serious revs.
Well, I guess it would still have to turn some serious revs...

but I agree there's no set answer to the question.
 
most likely will be the one in joliet IL. n some in southwest michigan, im shooten for the6000-6500 rpm range, dont think the 440s can handle too many revs.
 
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