[miketen07]

ok so i own a total of (3) dodge rams i got 1 2010 crew big horn 2wd hemi with a 3.92 gears and a lsd i gave my 2011 dodge small back doors 4.7L to my little brother and i drive my 2010 crew cab big horn hemi with 3.21 gears and a open rear end. i line up with just about everything. the 3.92 truck used to be the quickest of the bunch until i bought a diablo. the 3.21 truck barley stood up with the 91oct tune. then i rasied the shift points to 5900rpm and now the 3.21 walks the 3.92 truck. i raced my cousins 2009 little back door hemi on 17's with flowmaster exhaust and k&n filter and he does stand a chance. i raced a 2004 duramx crew with edge evo,afe intake, and 5inch turbo back exhaust and we stould fender to fender and he was on his highest tune. i thought i met my match thow against a single cab 2001 silverado with a 5.3L 2wd shortbed with long tube headers,intake,tune,exhaust,cam,and a stall converter and 4.10 gears. we hit it at 30-35 mph and everytime i had him by a few feet until 115mph so far this truck has 15k miles runs great has 20in wheels and with tuner gets about 22mpg on the highway. i know alot of you guys hate racing in your 3.21 gears but top end there awsome. but just to add i hate racing from a dead my tuck dosent pull until 4k rpm.

 

[TheSatinPumpkin]

Sounds good..................

ok so i own a total of (3) dodge rams i got 1 2010 crew big horn 2wd hemi with a 3.92 gears and a lsd i gave my 2011 dodge small back doors 4.7L to my little brother and i drive my 2010 crew cab big horn hemi with 3.21 gears and a open rear end. i line up with just about everything. the 3.92 truck used to be the quickest of the bunch until i bought a diablo. the 3.21 truck barley stood up with the 91oct tune. then i rasied the shift points to 5900rpm and now the 3.21 walks the 3.92 truck. i raced my cousins 2009 little back door hemi on 17's with flowmaster exhaust and k&n filter and he does stand a chance. i raced a 2004 duramx crew with edge evo,afe intake, and 5inch turbo back exhaust and we stould fender to fender and he was on his highest tune. i thought i met my match thow against a single cab 2001 silverado with a 5.3L 2wd shortbed with long tube headers,intake,tune,exhaust,cam,and a stall converter and 4.10 gears. we hit it at 30-35 mph and everytime i had him by a few feet until 115mph so far this truck has 15k miles runs great has 20in wheels and with tuner gets about 22mpg on the highway. i know alot of you guys hate racing in your 3.21 gears but top end there awsome. but just to add i hate racing from a dead my tuck dosent pull until 4k rpm.

 

[chefred112]

too bad you don't live in the same town that kay or i live in...we'd give you a little run for your money:smiley_thumbs_up:

 

[snrusnak]

^ makes sense, the more elapsed time you can keep the motor in the powerband the more it will pull! 350ft lbs at 1000rpm pulls the same as 350ft lb at 5000rpm. The longer period of time you are in a range with the most torque the better! This is very interesting, I was looking at swapping my 3.55 to 4.56 but am afraid of over gearing it.... (I have 4.7L).

I believe timmy also runs a quick 1/4 mile with 3.21's....

 

[CHVYKLR]

if numerically lower gears were the answer everyone at the track would be swapping to 'em but it is awesome the DSP and shift point mod had such a huge effect.

rusnak, i'd still do the gear swap...numerically higher gears are a "torque multiplier"

 

[snrusnak]

if numerically lower gears were the answer everyone at the track would be swapping to 'em but it is awesome the DSP and shift point mod had such a huge effect.

rusnak, i'd still do the gear swap...numerically higher gears are a "torque multiplier"

I understand, but there is a balance. It's possible for a vehicle with lower numerical gearing to run a faster 1/4 mile than with higher gearing....all else being equal. You want to gear it so you spend the most time at rpm's where the engine puts out the most torque....

 

[chefred112]

^ makes sense, the more elapsed time you can keep the motor in the powerband the more it will pull! 350ft lbs at 1000rpm pulls the same as 350ft lb at 5000rpm. The longer period of time you are in a range with the most torque the better! This is very interesting, I was looking at swapping my 3.55 to 4.56 but am afraid of over gearing it.... (I have 4.7L).

I believe timmy also runs a quick 1/4 mile with 3.21's....

you can never over gear a 4.7, I run 4.56's on 30" street tires on 17's and never think that I don't have enough gear...and i still get good gas mileage..

 

[snrusnak]

you can never over gear a 4.7, I run 4.56's on 30" street tires on 17's and never think that I don't have enough gear...and i still get good gas mileage..

I have a desktop dyno and drag time program, and according to the program the same setup with 4.10 runs a faster 1/4 mile by like 1 tenth.

I'm debating between 4.10 and 4.56..... How is your gas mileage with the 4.56...primarily highway mileage?

 

[Rayminator]

Run it at the track, and see how disappointed you are.

It may have a sweet spot or two, on the street. But from a dig, it will be a pooch.

 

[916Timmy]

I called about 4.56's the other day, and I guess they need to clearance the housing a little...is that bad?

I also have a 3.21 truck, running 15.3 @ 94.5 when its 95 degrees out

 

[CHVYKLR]

Timmy, running 4.10s with a 30" tire will be the same as running 4.56s with your factory tires. Plus you shave a little bit of unsprung/rotational weight.

 

[916Timmy]

I was wanting to run 4.56 gears with 27" tall tires 4.10s would be better on the highway though

 

[snrusnak]

It is possible to run faster in the 1/4 mile with lower numerical gearing. Higher numerical gearing acts as a torque multiplier, but depending on the torque curve of the engine, and the gearing of the transmission, you may have an advantage with lower numerical gearing by spending more time in a gear where you would be at an rpm producing more torque for more time...

You would have to figure out shift points, and what rpm you would be at after the shift, then find the area under the torque curve between that rpm and max rpm at shift, and do this for each gear while in the 1/4 mile, and compare with different rear end ratios, and the one with the largest area would be fastest. The more area means that it would be putting out more torque for the most time. I think this is how the program I have works, I don't know how else it would do it. I have a feeling 4.1 would run faster than 4.56 with the 545rfe (especially with the hemi). According to the program I have, the 4.1 run faster than 4.56 with the 4.7L. The benefit of the 4.56 is that you would have more low end on the street...

If the torque curve of the engine were perfectly flat over any rpm, higher numerical gearing would always be better....

 

[TheSatinPumpkin]

27" tires for the street... Holy Smokers!!!.

I was wanting to run 4.56 gears with 27" tall tires 4.10s would be better on the highway though

 

[916Timmy]

Just the track! I'll keep the 33s to save gas!

 

[TheSatinPumpkin]

Gotchaaa.......

 

[RadioFlyer]

I agree with everyone about the atuomatics and low gears being better for the track. But I had lots of high to low 13 sec street cars with 3.23 gears. Had three of my good ones at the same time and my 4 speed 383/3.23 Chally was quicker than my 383 276/485 auto/3.91 Bee. You would think the Chally would have been slower out the hole with a 300/558 and 3.23 gears but it wasn't. First start and track day was with the 3.23's low 13's I did swap it out for a 3.91 and got it in the 12's but still...had another Chally too. Not too fast by todays standards but good for the 70/80's Had a Camaro/Cuda at the same time too, both full race with 5.13's lenco 5 speeds. Too bad the Nag wasn't around then. BTW...I met my wife on the highway in her 72 400 Grand Sport Torino. I hooked both her and her car and later her dads 70 428 Cobra Jet Torino. Their whole family raced Nascar...all Fords, it was a marrige in heaven for me!

 

[RadioFlyer]

It is possible to run faster in the 1/4 mile with lower numerical gearing. Higher numerical gearing acts as a torque multiplier, but depending on the torque curve of the engine, and the gearing of the transmission, you may have an advantage with lower numerical gearing by spending more time in a gear where you would be at an rpm producing more torque for more time...

You would have to figure out shift points, and what rpm you would be at after the shift, then find the area under the torque curve between that rpm and max rpm at shift, and do this for each gear while in the 1/4 mile, and compare with different rear end ratios, and the one with the largest area would be fastest. The more area means that it would be putting out more torque for the most time. I think this is how the program I have works, I don't know how else it would do it. I have a feeling 4.1 would run faster than 4.56 with the 545rfe (especially with the hemi). According to the program I have, the 4.1 run faster than 4.56 with the 4.7L. The benefit of the 4.56 is that you would have more low end on the street...

If the torque curve of the engine were perfectly flat over any rpm, higher numerical gearing would always be better....

4.10 would be a better all around gear for you, I wouldn't go 4.56 being that you use it as a family truck. edit: I want to share my experience using 456 gears on the street. If you do use these gears and you can't hook up with them, the same 400hp truck, same everything side by side with 3.92/4.10 gears is going to walk away from you. The only way they will benifit you is if they hook up and that's hard to do on the the street with 4.56 gears. I'm not sure how it will affect these crappy traction control rearends, but I'm sure about it without them. So if you're using your truck for every day driving I wouldn't waist my time on 4.56's. It's a different story if it's the other way around and you use it mainly for racing on the track with some good rubber. Your truck may look good sliding all over the place but that's about it.

 

[snrusnak]

I agree, I'd go 4.10. You can match your tire size for the track to wind out the rpm's without hitting 4th gear, and run just as fast as if you had 4.56 and matched your tire size to do the same...

 

[RadioFlyer]

I agree, I'd go 4.10. You can match your tire size for the track to wind out the rpm's without hitting 4th gear, and run just as fast as if you had 4.56 and matched your tire size to do the same...

Not sure about yours snrusnak but it ought to be pretty much the same. Unless you Hemi is cammed with a decent mid to high range torquer, 4.56 is overkill for a stock Hemi. I'm talking about a cam with at least a 250 duration even better a 276 using 30 to 31" tires. That would give the extra top end torque you would need with the 4.56 gear. You could prolly go with a 4.88 if you were using the 392 stroker 584/554 279/285 cam