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3.73 gears in 2011-2014 charger srt8?

Charger 
16K views 36 replies 9 participants last post by  Hemissary 
#1 ·
Anybody done this?? Looking into this or 3.55s?This 5 speed nag1 tranny needs some lower gears.

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#2 ·
The factory did 3.92's in 2011 on the Charger Mopar 11.

That's about 3,100 rpm at 80 so maybe a little much, the 3.73 about 150 rpm less.

Should rip in the city but will tach up a bit on the highway.

Your 3.06 in 4th will turn about the same revs as the 3.73 in 5th so good way to see if you can live with the highway rpm before making the swap.




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#4 ·
The factory did 3.92's in 2011 on the Charger Mopar 11.

That's about 3,100 rpm at 80 so maybe a little much, the 3.73 about 150 rpm less.

Should rip in the city but will tach up a bit on the highway.

Your 3.06 in 4th will turn about the same revs as the 3.73 in 5th so good way to see if you can live with the highway rpm before making the swap.

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Thanks for that info. I'll try that

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#5 ·
TN,
Did you ever have any issues with any of the swaps? Can you just change the gears or have to buy the whole thing?
2 more questions :
-where you get them?
-was it a noticeable difference between the 373 and the 306?

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#6 · (Edited)
Time to bust an ongoing wive's tale...

Your engine could NOT care less at what rpm it cruises at on a highway. At legal speeds, there is absolutely zero(!) damage occurring. Those that say otherwise - for them - its a touchie-feelie thing that the love of their life, their engine, is somehow being compromised. It isn't.

Therefore; pick a ratio and buy it. I worked my way through four units to arrive at 3.92:1 with different engines. The performance gains are self-evident. It takes existing SAE torque and multiplies it by that ratio! Guess what that means. In other words; bragging about some high HP value means nothing. Torque does the work in these pigs. Without putting too fine a point on it; 3.92s behind an extremely healthy 440 puts the Magnum in a category where very few marques can compete.

Using my right foot to modulate the gas pedal means I have infinite range adjustment between idle and WOT (1000HP means f!ck-all if you can't properly apply it).
 
#8 ·
Personally I would not like anything lower than the 3.73. I feel it is at the edge of what is comfortable on an interstate IMO. The 4.30 caused my engine to start overheating at constant speeds above 70 mph.

The 3.73 and 3.91 can be purchased from your dealer or look for a used unit. You might talk with BNFY. I would advise buying the whole differential.
 
#9 ·
Man I really did look at the 3.91 but people say it’s to much. I guess their cheaper for some reason also, I’m told 1st gear would be useless in my ‘12 superbee.


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#15 ·
Man I really did look at the 3.91 but people say it's to much. I guess their cheaper for some reason also, I'm told 1st gear would be useless in my '12 superbee.

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Who are "they"?

"They" are the same worry-warts I was referring to above...emotionally driven that the engine is somehow being "over-revved" :^)
 
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#11 ·
I got a guy works at dealership and quoted me 28 or $2900. Can’t remember now. Seems pricey but I really would like to do something like this if there’s good feedback about doing this.


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#16 ·
I got a guy works at dealership and quoted me 28 or $2900. Can't remember now. Seems pricey but I really would like to do something like this if there's good feedback about doing this.

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Major cost difference between the two; the 3.92 being significantly less money. Someone on here a while back bought a pallet full of 226mm's from a dealership closure.
 
#12 ·
Had 3.91 in my car for several years.
5.7 cam/nitrous auto car. Lots of fun on street and strip. Went to a custom 4.10.
You will notice a big difference going 3.73 or 3.91 swap from a 3.06, it’s worth it.

P.S. first gear is only useless if you don’t have a good tire and spin, first gear and 3.91s get you out of the hole faster than the guy next to you.


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#13 ·
One has to give up the idea of going fast (>175mph). Its a foolhardy / stupid idea on public roads any way ya look at it.

A small price to pay for the outright gain in acceleration (rate of).
 
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#14 ·
Anybody got a link to where the cheapest place to purchase?


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#18 ·
Your first gear will be fine with shorter gears (numerically higher). There are cars with way more torque than ours running old ass torqflites and 727s with 4.10s or more and they hook up.

The people who say "first gear will be useless" are full of it. They can't drive. Don't listen to those grannies.

The 15+ 6.4s have both more torque AND more first gear than your car, and they hook up. Traction is a function of driver mod first, and tires second. I can hook up first gear in my 70 Charger with a 580" big block, a hemi four speed, and 4.10s out back (that's 11.5x gear multiplication being turned by 700ft/lbs of torque).

I just put 3.91s in my heads/cam RT, and the only thing I wish I had now is MORE TORQUE! Don't fear the gear.

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#19 · (Edited)
Your first gear will be fine with shorter gears (numerically higher). There are cars with way more torque than ours running old ass torqflites and 727s with 4.10s or more and they hook up.

The people who say "first gear will be useless" are full of it. They can't drive. Don't listen to those grannies.

The 15+ 6.4s have both more torque AND more first gear than your car, and they hook up. Traction is a function of driver mod first, and tires second. I can hook up first gear in my 70 Charger with a 580" big block, a hemi four speed, and 4.10s out back (that's 11.5x gear multiplication being turned by 700ft/lbs of torque).

I just put 3.91s in my heads/cam RT, and the only thing I wish I had now is MORE TORQUE! Don't fear the gear.

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Two things that helped drastically with 1st gear, other than better tires:

1. If you have throttle boost enabled on your tuner, turn it back to zero. That will give your more "resolution" to be able to modulate the throttle better, versus having the booster setting multiply your input.

2. Hit the traction control button to turn it off. Maybe its just my vehicle but the traction control initiates an artificial loss off traction when I get into the throttle a bit in 1st. It felt like I hit some ice but its the middle of summer in Florida. Turning it off by just hitting the button once helped a lot. The rear end still gets a bit loose but at least it stays straight and power is delivered properly.
 
#23 ·
Given different rear gear ratios available, max rpm and applied tire diameter (need to enter your specifics), here's a Gear Ratio Calculator.

NAG1 transmission ratios to enter:
1st: 3.59
2nd: 2.19
3rd: 1.41
4th: 1.00
5th: 0.83
 
#28 ·
Here are a few comparisons:







 
#37 · (Edited)
You might be able to confirm by turning tightly (full lock) at low speed (first one way - then other).
 
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