[Keith E.]

1. I plan to purchase a '15 Charger with a 392. I would like to hear from anyone that's running 3.55s specifically and any other differential gear sets.

2. Also would any '15 392 owners do or order any other drivetrain items?

Mods please move if needed. I put it here hoping for more traffic.

Thanks,
Keith

 

[500CIDV8]

I doubt that anyone has gone that far with a 2015 yet, haven't seen it yet anyway. My first thought is that 1st gear is so short on these 8 speeds that you have to be on your game a little to not bounce it off the limiter with stock gears.

 

[jim383]

I dont think any1 out there makes a 3.55 gear set. If they did the 3.55 would help your 1/8 and 1/4 mile times but hurt your freeway MPG. If your going to try and get 3.55 you might as well go to 3.92.

 

[Rogue 11]

I had the 3.92 gears in my Mopar 11. While they were great for burning the tires, I actually think it was too much gear for the car at the track. IMHO the 3.55 would have been the all around ideal gear for that car. Having said that, my new Scat Pack has the 8 speed transmission and I would be reluctant to change to gearing in the rear end. It has a fairly low 1st gear already.

 

[Keith E.]

Guys I appreciate the replies. The reason that I was asking about the 3.55s is that I have a '14 R/T with 3.06s that turns a touch over 2k @ 70mph while getting a combined 20-23mpg. My local dealer let me test drive a '15 R/T and it was turning a touch over1.5k @ 70mph. Since the Scat Pack would have to be ordered I was considering 3.55s from the factory. As a side note, yesterday when I went to place the order I was told by the dealer that there will be no more orders accepted until the '16 model year vehicles. This had noted here in another thread.

Rogue, is there anything thing that you'd do different on your '15 SP?

I'm now going to be on the hunt for a '15 Scat Pack until they start taking orders for the '16s.

Thanks,
Keith

 

[michiganpat]

Guys I appreciate the replies. The reason that I was asking about the 3.55s is that I have a '14 R/T with 3.06s that turns a touch over 2k @ 70mph while getting a combined 20-23mpg. My local dealer let me test drive a '15 R/T and it was turning a touch over1.5k @ 70mph. Since the Scat Pack would have to be ordered I was considering 3.55s from the factory. As a side note, yesterday when I went to place the order I was told by the dealer that there will be no more orders accepted until the '16 model year vehicles. This had noted here in another thread.

Rogue, is there anything thing that you'd do different on your '15 SP?

I'm now going to be on the hunt for a '15 Scat Pack until they start taking orders for the '16s.

Thanks,
Keith

you have to look at the overall gear ratios....1st gear in your '14's A580 is 3.59:1, so your overall 1st gear ratio is 3.59*3.06=10.99:1. going to a 3.55 would jump that up to 12.74:1. 1st gear in the 8HP70 is 4.71:1, so overall first gear with 2.65's would be 12.48:1, with 3.06's would be 14.41:1 and with 3.55's would be 16.72:1 and would make first gear completely useless....

 

[Black-N-Tan]

you have to look at the overall gear ratios....1st gear in your '14's A580 is 3.59:1, so your overall 1st gear ratio is 3.59*3.06=10.99:1. going to a 3.55 would jump that up to 12.74:1. 1st gear in the 8HP70 is 4.71:1, so overall first gear with 2.65's would be 12.48:1, with 3.06's would be 14.41:1 and with 3.55's would be 16.72:1 and would make first gear completely useless....

In theory, yes, however, with decent radials the only worry he'll have is twisting the driveshaft. :grin2:

 

[Rogue 11]

Keith E., if you were looking to change the gears in your '14 to a set of 3.55's I would say that you would enjoy the switch. I believe it is a fairly expensive modification so you would have to decide if the cost is worth the reward though.

My understanding is the new SP's have a 230 mm rear end (even larger than the 226 mm in my Mopar 11) and is only offered in a 3.09 gear ratio. I haven't seen anyone offering different ratios in the aftermarket either.

I haven't put a bunch of miles on my SP yet, but so far I am loving everything about the car. I was very impressed at how well my M11 ran and drove but it took about 1 block in the SP to realize this car will run circles around the M11. I'd recommend you drive the 392c.i. with the 8 speed before thinking about changing the gears. First gear in the SP feels a lot like 1st gear in the M11 with the 3.92 gears.

A final note: The M11 ran close to 3,000 rpm's at 70 mph. After driving the SP (that turns way less RPM's) I would say the SP will be more fun and comfortable to drive on extended trips. Always felt like I needed another gear in the M11 out on the highway.

Hope that helps.

 

[Keith E.]

Guys,

Once again I'd like to thank you for all of the replies. I was actually able to place an order for a '15 Charger Scat Pack yesterday through Bob. We'll see how it feels with the stock gearing and adjust if needed.

Thanks,
Keith

 

[Rogue 11]

Congratulations on your order. I hope you don't have to wait too long for it to arrive.

 

[Thrashie]

sheesh 3.55 (currently) & 3.92 (past 2 trucks) is what I have in my truck..gonna tow with that thing? heh

 

[tacamo01]

Congrats on the order! You will have to wait until tuning is available on the 15's before you even think about changing gears. It took a long time for the new MY11 tuning to come out. It is not just a simple change of the differential. Tuning took almost 2 years for the 2011/2012's and I suspect that with this new redesign it will take about as long. This is something that Dodge does every redesign or bump in power.

 

[Vogelsong]

sheesh 3.55 (currently) & 3.92 (past 2 trucks) is what I have in my truck..gonna tow with that thing? heh

I love 3.55's in a strong running street car.

 

[Blaquesmith]

I have a '12 Charger RT Plus with 3.55 gears (yeah, I know its slightly off topic), but I love it! So much better than 2.65 open diff. Now its like sex with a ugly woman, she gives it all she got so you will come back for more, lol :laugh2:

Congrats on your order, make sure you post pics and let us know how it drives...

 

[AvsBest]

I agree with the rest, it may just be too much gears for the 392. I had the Mopar 11 before and I really likes the 3.92 gears but put the SRT with the 8 speed and you won't be able to Hook up in 1st gear I'm afraid. SRT: Don't touch. RT: Go for it (On the 5 speed, haven't tried the 5.7 on the 8 speed)

 

[tacamo01]

With the new 8 speed and first gear at 4.71, second at 3.14 and 3rd at 2.10 ratios, with a 6000 rpm redline you will run out of gears with a 3.92 rear at:

1st: 28 mph
2nd: 42 mph
3rd: 62 mph

Not good at all.

http://www.f-body.org/gears/

 

[Keith E.]

Keith E., if you were looking to change the gears in your '14 to a set of 3.55's I would say that you would enjoy the switch. I believe it is a fairly expensive modification so you would have to decide if the cost is worth the reward though.

My understanding is the new SP's have a 230 mm rear end (even larger than the 226 mm in my Mopar 11) and is only offered in a 3.09 gear ratio. I haven't seen anyone offering different ratios in the aftermarket either.

I haven't put a bunch of miles on my SP yet, but so far I am loving everything about the car. I was very impressed at how well my M11 ran and drove but it took about 1 block in the SP to realize this car will run circles around the M11. I'd recommend you drive the 392c.i. with the 8 speed before thinking about changing the gears. First gear in the SP feels a lot like 1st gear in the M11 with the 3.92 gears.

A final note: The M11 ran close to 3,000 rpm's at 70 mph. After driving the SP (that turns way less RPM's) I would say the SP will be more fun and comfortable to drive on extended trips. Always felt like I needed another gear in the M11 out on the highway.

Hope that helps.

Rogue11,

What rpm are you turning at 70mph?

Thanks,
Keith

 

[tacamo01]

Rogue11,

What rpm are you turning at 70mph?

Thanks,
Keith

Use this calculator to find the rpm/speed in any gear. Gears for the 8 speed:
Spread Ratio: First 4.71, Second 3.14, Third 2.10, Fourth 1.67, Fifth 1.29, Sixth 1.00, Seventh 0.84, Eighth 0.67, Final Gear ratio:3.09

http://www.f-body.org/gears/

Now compare that to the old NAG1 5 Speed:

First: 3.59, Second: 2.19, Third: 1.41, Fourth: 1.0, 5th: 0.83 Final 3.06

 

[Keith E.]

Use this calculator to find the rpm/speed in any gear. Gears for the 8 speed:
Spread Ratio: First 4.71, Second 3.14, Third 2.10, Fourth 1.67, Fifth 1.29, Sixth 1.00, Seventh 0.84, Eighth 0.67, Final Gear ratio:3.09

http://www.f-body.org/gears/

Now compare that to the old NAG1 5 Speed:

First: 3.59, Second: 2.19, Third: 1.41, Fourth: 1.0, 5th: 0.83 Final 3.06

tacamo01,

Thanks for the info. The reason that I ask is my local dealership let me drive a '15 RT Charger. I didn't check the sticker for diff ratio and it was just loping along, 1500 rpm @ 70mph. That's the reason for my original post about 3.55s with a '15 392.

Thanks,
Keith

 

[Rogue 11]

Rogue11,

What rpm are you turning at 70mph?

Thanks,
Keith

It ran close to 3,000 rpm's at 70. Officially it might have been 2,850, but that is still screaming.

As I put more miles on my SP, I am enjoying the set up more and more. It will be awhile before I will take it to the track to see how many gears in uses in the quarter mile. But my Mopar 11 shifted into 4th gear way too early IMHO. It was a beast off the line, but I always felt that it did a nose dive going into 4th at about 2/3 the way down the track. I continually ran better times as I learned to drive it better. My PB was a 13.26 this last winter.