2.76 vs 3.23 vs 3.55

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74 dart sport said:
Tire height is 23.4 inches ( yeah, I know . Really small lol) . Fair amount of time on freeway is ~10 ~ times a week.
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With what you say here, you are best off with the 2.71's that you have now. Here in Nebraska, Interstate is 75mph with most running 80.. 3.23's even suck at those speeds without an OD at least. With that short of tire you probably even need 2.45's, real dog though. On a 300 mile jaunt on the freeway, you will be sorry you have anything else than what you have. Just my opinion. I have a 67 Dart with a 273 auto with 2.71 gears, a 71 Polara with a 440 auto and 2.76 gears and a 69 Coronet R/T with a 440 that has 3.23 gears, that I'm going to install 2.76 gears when it gets a new engine. Sometimes you have to give up the tire burning for a little sanity. I drive my cars on the Interstate regularly. I don't like everyone passing my old cars, and they don't! Good luck with your decision.
 
Dayam not much love for my 4.56's ????


Glad I'm old enough to not care.

Wait wait wait...my 72 Demon in high school had 4.56's too. It was my late night money maker.
 
yellow rose said:
Dayam not much love for my 4.56's ????


Glad I'm old enough to not care.

Wait wait wait...my 72 Demon in high school had 4.56's too. It was my late night money maker.
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Nope. I put thousands of miles on my car every year on the freeway, which means doing at least 70mph, and realistically more like 75, sustained for longer periods of time. With my 26" tall tires I'd be turning 4100 rpm to do 70. You're not going to do that for a couple hours straight.

Maybe if you ran 30" tall tires, or rarely drove faster than 55 or 60, or never went on trips longer than 20 or 30 minutes. Otherwise they're just a PITA. And you still have to hook, and with 4.56's and street tires that's no small feat in itself. And I'm not talking DOT drag radials, because those aren't practical for higher mileage either.
 
what size tire is 23.4?? buy some taller tires and a 2nd set of wheels and go 3.21 or 3.55 and swap tires and wheels depending on around town or hiway
 
for a teen, Id like the 355's for the engine rpm, but a 360 could turn some 3.23's easily.
 
..seems most prefer 3.55 but...
Not a good highway gear and not a good 1/4 mile gear
3.23 all the way for me,but i don't race at the strip or it would be 4.10
 
72bluNblu said:
Nope. I put thousands of miles on my car every year on the freeway, which means doing at least 70mph, and realistically more like 75, sustained for longer periods of time. With my 26" tall tires I'd be turning 4100 rpm to do 70. You're not going to do that for a couple hours straight.

Maybe if you ran 30" tall tires, or rarely drove faster than 55 or 60, or never went on trips longer than 20 or 30 minutes. Otherwise they're just a PITA. And you still have to hook, and with 4.56's and street tires that's no small feat in itself. And I'm not talking DOT drag radials, because those aren't practical for higher mileage either.
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Yeah. I am going to make a few 300 mile trips out to Havasu at 80-85 mph so I might kill my engine with revs that high in the 100 degree weather lol
 
Do you guys think 3.23 s with a lsd would be pretty good off the line (for a first car, I'm not even 16 yet). I don't need brutal acceleration, I don't want to get in a crash or get pulled over lol
 
with the tiny little tires you have 3.23's won't be horrible. In fact with those tires I wouldn't even recommend 3.55's if you plan on hitting 80 on the freeway, 3.55's and those tires would mean turning 4,100 rpm to hit 80. Even the 3.23's will put you over 3,700 rpm at 80. Anything much over 3,500 gets old pretty fast.

Off the line acceleration is cool, but if you're driving your car on the street and are planning to take it on 300 mile trips the cruising RPM is much more important. Sure, you could run 4.56's and make it a burn out machine, but you'll then be driving to Havasu at 65 mph listening to the engine scream and watching your gas gauge plummet the whole way.
 
Could always do a tranny swap also with lower 1st 2nd gears and for your 300 mile trips you always swap back in the 2.76 gears.
 
Lustle said:
Define "fair amount" of time on the freeway?

3.55 is generally seen as the best "compromise" gearset for highway/city driving. 4.10 can be as well. Can't speak as to RPM until we know your rear tire height. 2.76 - 3.55 is gunna make a huge difference. Your 318 will feel a lot bigger!
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I would think 3.23's are the best compromise.
 
If yur still running the stock convertor; then just get a higher stall; that will make way more difference to your take off.
But honestly, 23.5 x15s in wheelhouses that should accept 28s? And your 67
(Modifications: RV cam , zero decked, 4 bbl, headers, true dual exhaust (no cross pipe), and an open diff), can't even squawk one of them?
I'd guess you don't have much cylinder pressure so that's where I'd start.
What you want is; 185psi, lol, that will wake that 318 right the heck up.
Second best with closed chamber 67 heads would be ~160/165psi.
If it can't make even 135psi, well, put a 2800TC in it and, just drive it.
If you're at over 1000ft elevation, stuck with low pressure, yur screwed anyway you look at it.

BTW your 23.5s are already ~17% shorter than 27s so that makes your cruising rpm similarly 17% higher. 3.23s would put it 17% up so, you are already running nearly the equivalent of 3.23s and 27s, and you still can't squawk even one tire? that is bizarre, something is wrong with your combo.

your Cruise rpm@65mph should be;
with 2.76s and 23.5s; about 2570@zero-slip, perhaps 2650 on the tach.
with 3.23s and 23.5s; about 3000@zero-slip, perhaps 3100 on the tach
with 3.55s and 23.5s; about 3300@zero-slip, perhaps 3400 on the tach.

From all I know, every 2% increase in cruise rpm, will lose you 1% in fuel economy with no other changes. So then, a 12% increase in cruise rpm might be a 6% loss in economy , If your Sport is making 18mpgs with the 2.76s, then expect 16.9 with 3.23s, and 15.7 with the 3.55s . This is in steady-state hiway usage. Around town, it will be worse, because of stop and go, plus accelerations up to speed. a lot worse.

I would stuff a 2800 convertor in there in a heartbeat.
Well, I'd also get rid of those 23.5s lol.
225/70-15s are about 27.4, and so, will reduce your current cruise rpm to
23.5/27.4= 85.77% or 2370rpm. To get the performance back to where you now are, would require a gear of 2.76/85.77%= ~3.23s to where you are now.

Here's the trick.
If a 2800 TC gets your engine up the torque curve say 50 ftlbs, then at 2800rpm that is 27horsepower. That is the cheapest, easiest, fastest way to get 27 stinking normally aspirated horsepower, down low, bar none.
But it doesn't solve your dead duck 318 that can't even squawk one tire, at the current stall.
Again
I would start with a compression test, and a timing system evaluation.
Maybe your cam has gone flat.
maybe the rings are bad.
maybe the distributor is seized.
But for sure something is wrong.
 
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