Anyone with a hemi, swaped from 3.92 gears to 4.56's?

[truckin151]

I think thats not right there AF & VA. If you were to take two of the same trucks, one with 3.55's and one with 4.56's and lined them up on a perfectly flat loooooooong stretch of road and had them run till they couldn't go any faster, the truck with the 4.56's will get up to speed faster however the truck with the 3.55's will end up with the higher top speed (not by much though). Will it be noticeable in day to day driving no, but in a top speed run you will see the difference.

RPM's do not equal speed. Case in point, me runnning at 70mph before and after the gear swap are two completely different rpm ranges. Before with the 3.92's at 70mph it was right around 1900rpms and with them I am running around 2300rpms.

 

[Ramunit]

Trup, read carefully, You will gain some top end also because with the better gearing the engine can turn turn up a higher rpm. The stock gearing doesn't allow the engine to top out in high gear. With a 4:56 /4:10 you can spin the engine up faster and to a higher rpm regaining the speed that couldn't be achieved with the stock gear. There is NO down side.

X2 except I can think of one downside. Because you can spin the engine up faster and into a higher rpm the stock shift points are gonna come quicker at part throttle. (I didn't like that). My experience was at part throttle I was ripping through 1-4up in no time. The remedy is Superchips trans tuning, with the ability to raise and adjust part throttle shift points the sucka pulls like a ***** ape. IMO SC trans tune, torque management adjustment and 4.56's make these trucks scream by keep it in the powerband with just a touch of the pedal at PT.

 

[Redtruck-VA]

I think thats not right there AF & VA. If you were to take two of the same trucks, one with 3.55's and one with 4.56's and lined them up on a perfectly flat loooooooong stretch of road and had them run till they couldn't go any faster, the truck with the 4.56's will get up to speed faster however the truck with the 3.55's will end up with the higher top speed (not by much though). Will it be noticeable in day to day driving no, but in a top speed run you will see the difference.

RPM's do not equal speed. Case in point, me runnning at 70mph before and after the gear swap are two completely different rpm ranges. Before with the 3.92's at 70mph it was right around 1900rpms and with them I am running around 2300rpms.

Maybe someone can do the math to figure how much horsepower is need to push a 5500 pound box up to 130 mph.

I will disagree, mostly because without the gearing I don't think the motor will make it into the higher rpm range mostly because of wind drag. With gearing I think the engine will turn up a higher rpm pulling the truck a little faster than with stock gearing. But, I'm just guessing.

 

[Trupiano]

Im pretty sure were right VA. Like I said, I dropped the gearing in my 06 yamaha r6, for more acceleration, and I lost some top speed. The engine only makes so much power. It's like a pedal bike, drop to a low gear and you can accelerate pretty fast...but you wont reach a very high top speed, because your feet can only pedal so fast(Your engine hp/tq represents how fast you can pedal). Raise the gear on your pedal bike, and you can up your speed, although you lose some power/acceleration. Pretty much the same idea in a truck/motorcycle/pedal bike... whatever.

 

[Redtruck-VA]

Im pretty sure were right VA. Like I said, I dropped the gearing in my 06 yamaha r6, for more acceleration, and I lost some top speed. The engine only makes so much power. It's like a pedal bike, drop to a low gear and you can accelerate pretty fast...but you wont reach a very high top speed, because your feet can only pedal so fast(Your engine hp/tq represents how fast you can pedal). Raise the gear on your pedal bike, and you can up your speed, although you lose some power/acceleration. Pretty much the same idea in a truck/motorcycle/pedal bike... whatever.

You may be right, I don't think our somewhat stock engines are capable of running out a 3:55 gear in a truck. And oh yeah, I have played with bikes for years and know what you are talking about. My project bike is a 97 V10 Moto Guzzi using a Daytona engine, 6 speed, extended swing arm and 6" rear wheel.

 

[RubberFrog]

Theoretically, trup is right. In real life though, the truck will hit an impassable wall of air long before it reaches any calculated max speed.

 

[glass3222]

Theoretically, trup is right. In real life though, the truck will hit an impassable wall of air long before it reaches any calculated max speed.

+1. The aerodynamics of our trucks is the limiting factor. You would need substantially more power to overcome it. That is why the STR10s top out at around 150. The gearing is not going to do much for top speed one way or the other, but I think with the aerodynamics and power range you will probably get an extra mph or 2 with 4.56s.

 

[MOPAR78]

Not yet, but I would go straight to the 4.56.

 

[SilentRamAD]

4.56's wont be if I lose 2-3 mpg! I'd rather go 4.10's if it'll increase my acceleration even a lil, without kamakazee'in my gas mileage. But I need some info/raw data to base this decision on.

Just wanted to get it off my chest, you got a truck >_< Not the best in the gas mileage department. Now don't get me wrong most things I do I try to keep mpg in mind but not at the top of the list.

On the good note, I went from 3.21 gears to 4.56's and have LOVED since. Gearing will always be my first thing I do in the future now.

Gained 2-3mpg overall city/highway combined. Acceleration was NIGHT and DAY. But then again you're going from a 3.92.

Now I just need a DTT or Auburn LSD to help with my open diff tire spin. DTT if I go lifted and Auburn if I drop the rear to level her out (Thanks Hammer for that info in the past).

 

[truckin151]

There was an argument/debate about this a while back on a different forum, but the concensus was if it was the same vehicle, same hp/tq with the only thing different being the gears, the vehicle with the shorter gears would be able to reach a higher top speed than the vehicle with taller gears. Doesn't really matter though since no one would want to try to peak out their vehicle, specially not a brick like we have.

Back on topic, trup, go with the 4.56's and dont look back. You'll be kicking yourself if you go with anything less.

 

[kay9]

Gears only do so much you still need the mods to keep you in the powerband. Mileage taken out of the equation but why is there not many folks running 4.88's in thier 2WD 1500? Esp' those with 30" or less tires. I understand for the 1/4 of course but for 100% street use, say 0-100 you can really cause some damage then stop after 100 lol. Or see how quick you can run all the way up to the end of 3rd.

 

[truckin151]

I think I have only heard of one other guy running 4.88's. I think they are just n unknown as not to many peopel have them in and everyone is running the 4.56 with great results

 

[kay9]

Which is why i just sold my 4.88's lol. I still want to put them in so bad but the buyers check just arrived today so once cleared then off they go

 

[Trupiano]

Ok, I guess its settled then! After the drop parts in october... 4.56's here I come! Thanks for the help/input/data gentleman!!!

 

[RubberFrog]

I would run 4.88s in a heartbeat if I had a 2 wheel drive.

 

[AF_Hemi]

^^^ditto

 

[Eaton]

...The remedy is Superchips trans tuning, with the ability to raise and adjust part throttle shift points the sucka pulls like a ***** ape. IMO SC trans tune, torque management adjustment and 4.56's make these trucks scream by keep it in the powerband with just a touch of the pedal at PT...

Scott, you're killing me here; I want to do 4.56's so bad! lol!

 

[Ramunit]

Scott, you're killing me here; I want to do 4.56's so bad! lol!

Matt, you of all people, I would have thought 4.56's were installed by now. As you know I highly recommend them

 

[milehighguy]

im reading your replies about switching from 3.92 to 4.56 gears... do you run bigger tires, or are they stock sized? thanks

 

[bigtigga84]

You can run stocks or bigger. Putting bigger tires with 3.55's dogs the engine. Next mod on my list hopefully, but i've read enough from the guru's to give you that advice fairly confidently lol.