rpm and gearing

[rt green]

rpm and gearing.  1\4 mile and street. what would the difference between 3.23,3.54 and 3.90 gearing with bfg 295/50r15 tires? 60ft time difference? mpg at 70mph? stock 69 charger RT 440 23 spline '70 4 speed. would like to only set this car up once, but I know you always test and tune. just trying to save some steps.  thanks for any response.  bruce

[Ghoste]

The rest of the combo has a real impact because of where the powerband is.

[rt green]

ok. for the subjects sake, stock with headers. MP ignition. six pack aluminum intake '69 center carb, '71 outer carbs.

[BSB67]

rpm and gearing.  1\4 mile and street. what would the difference between 3.23,3.54 and 3.90 gearing with bfg 295/50r15 tires? 60ft time difference? mpg at 70mph? stock 69 charger RT 440 23 spline '70 4 speed. would like to only set this car up once, but I know you always test and tune. just trying to save some steps.  thanks for any response.  bruce

Here is your secret for the day.  The gear ratio has very little impact on 1/4 et when using a traction limited, real street tire.

Use what you have and spend the $$$$ somewhere else.  After you have the car together and have driven it for awhile, and if you then feel strongly about changing the gear, go for it then.

[rt green]

BSB67- I love your bag of tricks. very interesting and I always learn something. thanks

[Ghoste]

I disagree.  I realize I have the tiniest fraction of your experience and knowledge and completely respect the times you run with a 3:23 but I think gearing does have a very noticeable impact even on a traction challenged car.

[c00nhunterjoe]

I disagree.  I realize I have the tiniest fraction of your experience and knowledge and completely respect the times you run with a 3:23 but I think gearing does have a very noticeable impact even on a traction challenged car.

based on the op's question; ie, bone stock 440 through manifolds with a 4 speed and real world street tires, i agree that you wont see much of any difference in this application.
   you cant bring a bone stock b body out hard on those tires..... its not going to work./ period. so the idea of steeper gears to launch the car is useless here since all you are going to do is make a smoke show with the tires. that particular combination will probably spin the tires from a roll.
   even so, lets assume he swaps the bfg's for a set of bias drag slicks and changes NOTHING else. i would bet it runs a 13.9 @102 (assuming he can shift).
now swap the 3.23's for the 3.91's and i bet the most you would see is a 13.8@ 102. the point of this is that the engine, being stock, doesn't make enough power, especially in the higher rpm, to need the steeper gears. it also has plenty of low end grunt to get it moving with the 3.23's thanks to the stock intake and cam.
  i hate to keep using my car as an example, but your FAST head topic is a good example. i am referring to the youtube link i posted of my car running a 13.21 @104 on street tires. i could bring it out on the converter @3000 and get a few chirps then mash it and take off. 60 foots were 2.2-2.4 depending on how much i could control the spin. fast forward to years later and i have the same motor with 4.30's in it. on street tires i was still running the same et's. step up to drag radials after i put the 4 speed in and i still cant get it to hook. the mph will always be the same since the rear gears don't add horsepower. they can drop your et depending mostly on how they affect your 60'. but they cant affect your 60' unless you have tires that will hold the car. roughly anything you cut off the 60 foot, doubles on your et.

[BSB67]

I disagree.  I realize I have the tiniest fraction of your experience and knowledge and completely respect the times you run with a 3:23 but I think gearing does have a very noticeable impact even on a traction challenged car.

I know that it is the common belief, but it simply does not have much impact.  About 0.07 to 0.10 in 60ft, and maybe 0.15 sec. in overall et.  Of course the mph stays the same.  Everyone gets caught up in the spinning their tires on the street that they think that their car is faster at the track.  The tire will only hold so much.  If you spin with 3.23, what do you think will happen with 3.91's?  There is a short period between the initial hit and roll out and about 80 ft out the higher numerical gear will pull ahead, usually less than a car length, then the remaining 1250 ft is an identical race as without the gear in high 12 second cars.  I have race so many guys that wanted to "catch me" by swapping a gear to surprise me at the track it is funny as the results are always the same.  

If you are going to spend money for a 0.10 in 60 ft time, buy a converter so it won't be miserable to drive on the highway.  

The beauty is that so few people know this, they are dumbfounded when they get spanked by a car with a 3.23, and even if you lose, you still win when you see the look on their faces when you tell them "3.23".  You're the one surprised by the 13.2 @ 104 with the 2.76, right?

Obviously, if you are going to do a bunch of suspension stuff, the difference will be greater.  But I'm talking about drivers.

[Dino]

Very interesting information.   

[1974dodgecharger]

I agree well said...I runthe 3.23 and people are surprised I have that back there...they call it, 'highway gears', but I can accelerate with them.....guess that hothckis suspension helps lay the rubber down 

[Ghoste]

 You're the one surprised by the 13.2 @ 104 with the 2.76, right?

Hell yeah, you aren't? 
You have to admit thats impressive.

[c00nhunterjoe]

 You're the one surprised by the 13.2 @ 104 with the 2.76, right?

Hell yeah, you aren't? 
You have to admit thats impressive.

I dont think mine is impressive.... i think 11.60's through manifolds on skinnys with a 3.23 is impressive.

[Ghoste]

I think both are for sure.

[c00nhunterjoe]

Lol. If you say so. Its just a run of the mill 383. There is really nothing special about it. Problem is, i want more speed and i cant do it with this engine because of the pistons and i dont want to do a total rebuild, so it stays a low 13- high 12 second car until i get the nuts up to put my 750 horse monster in it.... 

[ChargerST]

My plan is to swap my auto tranny for a 4-speed with a low 3.09 first and 1:1 final - paired with my current 3.23 rear end. I'm thinking that the 3.09 first should help the 60 times while still being very streetable with the highway rear end. Any thoughts? 440 btw

[Cooter]

Said it before, I'll say it again......you got enough motor, you don't need alotta gear.

[ChargerST]

Said it before, I'll say it again......you got enough motor, you don't need alotta gear.

haha, I know that I don't "need" the gear set Just wanted to know if there is a measurable difference between the two gear sets (2.66 first/3.23 vs. 3.09 first/3.23) - I have both sets at home.

[c00nhunterjoe]

Said it before, I'll say it again......you got enough motor, you don't need alotta gear.

haha, I know that I don't "need" the gear set Just wanted to know if there is a measurable difference between the two gear sets (2.66 first/3.23 vs. 3.09 first/3.23) - I have both sets at home.

On a street car you will see no difference. The 2.66 trans will pull about 20' further out before you shift to 2nd.

[moparsr2fast]

   Way " back in the day ", I owned a 74 charger se with a 440 engine. It was nothing special at the time, and the 440 was somewhat anemic. Ended up selling that car to purchase a 70 Charger RT/SE. It to was nothing outstanding at the time, just the factory stock 440 mag. She ran clean and strong, but again, just factory offering.  One day shortly after purchasing the 70, I had the fortune of running into the 74 out in the country. The person I sold the car to mentioned a gear swap to the 5:13 set, and wanted to run them to see what was what. We did both, a rolling start, and a dead start. Either way, we were neck to neck until I shifted out of 2nd into drive. Then I would shut him down badly as he was out of engine at that point. My 70 was running 3:23s. 

[Ghoste]

Yeah a switch like that with nothing else done to a stock 74 vintage 440 would be a pretty pointless waste.

[BSB67]

Said it before, I'll say it again......you got enough motor, you don't need alotta gear.

haha, I know that I don't "need" the gear set Just wanted to know if there is a measurable difference between the two gear sets (2.66 first/3.23 vs. 3.09 first/3.23) - I have both sets at home.

Define what you call measurable? Guys with slicks and high stall converters that are trying to improve there 60 ft from say a 1.5 to a 1.47 are usually pleased with the improvement in a lower 1st gear (autos).  On the street with a std tire, it will feel different, but measurable difference will be close to nil (again, because of the tire spin deal).  The other part people seem to overlook is that the 1-2 shift recovery is a lot different.  if you shift at 5500 rpm, the 2.66 will fall back to about 4000 rpm, the 3.09 will recover at about 3400 rpm.  (Second gear 1.93?) So you will be in second gear longer, and avg hp in second gear will be lower.  So if you actually gain something in 1st, you give some of it back in 2nd.  If you gain nothing in 1st, you'll still give some back in 2nd. Shaving a few hundreds in 60 ft on a drag car is usually worth it, and because they are usually "back in the converter" on the recovery, it does not hurt them at all in 2nd.

If you are all about spinning the tires, you will like it.

[ChargerST]

Said it before, I'll say it again......you got enough motor, you don't need alotta gear.

haha, I know that I don't "need" the gear set Just wanted to know if there is a measurable difference between the two gear sets (2.66 first/3.23 vs. 3.09 first/3.23) - I have both sets at home.

Define what you call measurable? Guys with slicks and high stall converters that are trying to improve there 60 ft from say a 1.5 to a 1.47 are usually pleased with the improvement in a lower 1st gear (autos).  On the street with a std tire, it will feel different, but measurable difference will be close to nil (again, because of the tire spin deal).  The other part people seem to overlook is that the 1-2 shift recovery is a lot different.  if you shift at 5500 rpm, the 2.66 will fall back to about 4000 rpm, the 3.09 will recover at about 3400 rpm.  (Second gear 1.93?) So you will be in second gear longer, and avg hp in second gear will be lower.  So if you actually gain something in 1st, you give some of it back in 2nd.  If you gain nothing in 1st, you'll still give some back in 2nd. Shaving a few hundreds in 60 ft on a drag car is usually worth it, and because they are usually "back in the converter" on the recovery, it does not hurt them at all in 2nd.

If you are all about spinning the tires, you will like it.

Thank you for the detailed explanation! I have enough parts to build two transmissions which I'm probably gonna do. Since my Charger is 95% street driven the feel is more important than 1 or 2 tenths in the quarter mile.

If second gear was something like 2.1 the ratio would be ideal (3.09, 2.1, 1.4, 1:1).

[Ghoste]

Well said.  I think many of us want our car to perform as well as it can but not at the expense of maximum enjoyment.  And of course that should be individual maximum enjoyment because I like to think we all enjoy our Chargers equally albeit in slightly different ways.

[moparnation74]

A lot of great cooments here on this topic, thanks for the info guys.

Best gears:  8 3/4  3.23
                 Dana 60  3.54

Ideal for street, highway, and track

Whenever you want more than those there are limitations on those three choices.

[Ghoste]

Why not a 3:55 for the 8.75 set?

[Dino]

That's what I had in mine and highway driving was less than amusing.   

I still have it though, I  may use those for the truetrac conversion with the T56.  My wife's T/A has 3:42 gears with a T56 and slightly shorter tires than mine and it is perfect.

[Ghoste]

I've had 3:91 and 4:10 sets in cars and they didn't bother me much.  I suppose it depends how much highway driving too. 

[c00nhunterjoe]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

[moparnation74]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

Or do you mean a 1/4 mile after every light, lol

[c00nhunterjoe]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

Or do you mean a 1/4 mile after every light, lol

I cruise my car everywhere, and decent distances too. A typical cruising weekend starts 25 miles away from home to get to the "main street" areas. I have no second thoughts driving 100 miles or so 1 way.
   I cant deny that everytime i come to a stop, i have to take off like im racing for pinks...lol

[1974dodgecharger]

U ever stop at a light and rehearse the fast and furious scene dialogue guy next to u?

[A383Wing]

you wanna play with gearing & tires first?

Go here  http://vexer.com/automotive-tools/speed-rpm-calculator

[Ghoste]

I love that you can select a 2nd gen Charger for the dash graphic. 

[firefighter3931]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

[Ghoste]

They were great in my last car too Ron for the same reason.  This one will likely end up as a 3:54 but I'll make my decision after I make the decision on some of the other variables.  There is a 3:23 in it now which is great for now and the Dana waiting to go in has a 4:10 as it sits but I don't know that I'll want that this time.

[rt green]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

what cam were you runnin?  was this a drag car?

[firefighter3931]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

what cam were you runnin?  was this a drag car?

Street/Strip car with 2 different engine combinations ;

(1) pump gas 446 with a big solid flat tappet cam

(2) pump gas 572 stroker with big solid roller cam


The best way to gear the car is to match the engine's powerband. If the engine is laboring at 2000 rpm the car will be inefficient. Keep the engine in the happy zone and it will perform much better. 

One of our members run's a 3.55 geared combo with 275/60 BFG's and on a recent visit he checked the milage and got 15mpg on the hwy on his trip out to visit me. Mild 440 build with a small Crower HDP hyd cam, dual plane intake manifold, HP exhaust manifolds and 750DP carb. He's done a lot of tuning using my wideband O2 meter and optimized the jetting and timing for maximum efficiency. The car cruises nicely at 2500 rpm on the hwy and it has descent fuel economy as well. 


Ron

[BSB67]

The best way to gear the car is to match the engine's powerband. If the engine is laboring at 2000 rpm the car will be inefficient. Keep the engine in the happy zone and it will perform much better. 

One of our members run's a 3.55 geared combo with 275/60 BFG's and on a recent visit he checked the milage and got 15mpg on the hwy on his trip out to visit me. Mild 440 build with a small Crower HDP hyd cam, dual plane intake manifold, HP exhaust manifolds and 750DP carb. He's done a lot of tuning using my wideband O2 meter and optimized the jetting and timing for maximum efficiency. The car cruises nicely at 2500 rpm on the hwy and it has descent fuel economy as well. 

Ron

I can never understand guys getting less than 10mpg.  That would have to be huge overlap cam and very short gear, and/or poorly tuned car.  14 -15 is about what I get with my 508 w/ 3.23s on the freeway.  It never gets less that 12 mpg and that is driving around town beating on it all the time.  That will include track time too.

[RECHRGD]

Years ago, I sold a 3.91 pig to the old DC.COM owner.  He replaced his 3.23's with them.  After driving it on the street, he thought the car would be at least .50 quicker and couldn't wait to hit the track.  It didn't change his times at all.....

[Cooter]

Top Fuel runs like 3second 1/4 mile with 300 gear. Sure, you won't cruise it 50 miles, but enough motor and gearing isn't as much a concern. Hence the reference to guys and 10 mpg. Most just have too big a carb, way too big of cam, doo-doo low comp. Bottom end with $3k worth of cyl. Heads AFTER a .030 piston I is installed cause they write checks instead of checkin behind that "cover his ass" machine shop owner.

VE is key. Many think they got a 10.5:1 440 back from machine shop, when in fact they got a really nicely machined, low comp. Turd.

[redmist]

I have 3.91 gears in my car, on street radial 285/40-R17's

I cross the traps in the 1/4 mile at 6000 RPM exactly...

Best time so far is a 13.2 @ 110 MPH.  Obviously I have a traction problem.

[Ghoste]

Ultimately your rearend gears are a lever and the ratio is just altering the pivot point.  Because the same load isn't being applied toone end of the lever (your engine) and the same results aren't desired at the opposite end (are you racing, are you looking for greatest mileage etc.) you can't put a one ratio is best for all to it.

[Paul G]

My 72 is about a 4100# car with 3.91 gears, 28" tall BFG 275/60-15 tires, and 2400 stahl. It ran 14.9 at 92 with 2.2 60'. It is a small block, less than 300 HP at the crank, dynod 230hp, 330'# at the wheels a few years ago. At the track it was still traction limited a little bit. I could not just nail the gas or the BFG's would spin. 

When this car was put together in 01 for the previous owner I suspect they chose the 3.91 gears because of the lack of power the small block would make. It moves pretty good stop light to stop light. But the steep gearing and low HP means it runs out of steam relatively quickly. It does not pull hard on the top end. I would imagine in this case the tall gearing has helped the low end city driving/street performance.