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Discussion Starter #1 (Edited)
Am I the only one not that impressed with the difference going from 3.06 open to 3.92 Getrag in an automatic R/T? I guess I'm so used to driving with 4.10's in my other car that it's just not a big deal. This is a list of what I like and don't like.

Like:
1. Power is there almost instantly
2. Can leave it in drive and always have power, no lugging around or shifting into a high gear during acceleration
3. Should drop my 1/4 mile time (obviously)

Don't like:
1. Exhaust tone doesn't sound anywhere near as badass as it did (higher RPM's)
2. Highway speed RPM
3. Not enough difference in acceleration to justify the fuel mileage decrease
4. Getrag humming sound
5. Was a B1TCH to install


Finally got a chance to floor it in manual mode today. First gear was spinning, but I guess wheel hopping? Tires were like "chirp chirp chirp chirp". Second gear screeched, and third gear took off. Gets to 100mph faster, but to be honest I'd rather have my original open 3.06 setup back in. I might end up swapping the Getrag gears for 3.55's sometime soon. Overall, not impressed.

I might just switch my Diablo 93 tune back to the factory 87 tune. The gears should make up for the difference, I really don't think the Diablo 93 tune does jack sh-t. Would turning MSD back on give me a couple more MPG with the 3.92 setup? Damn I miss the way my R/T sounded before the swap...


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Am I the only one not that impressed with the difference going from 3.06 open to 3.92 Getrag in an automatic R/T? I guess I'm so used to driving with 4.10's in my other car that it's just not a big deal. This is a list of what I like and don't like.

Like:
1. Power is there almost instantly
2. Can leave it in drive and always have power, no lugging around or shifting into a high gear during acceleration
3. Should drop my 1/4 mile time (obviously)

Don't like:
1. Exhaust tone doesn't sound anywhere near as badass as it did (higher RPM's)
2. Highway speed RPM
3. Not enough difference in acceleration to justify the fuel mileage decrease
4. Getrag humming sound
5. Was a B1TCH to install


Finally got a chance to floor it in manual mode today. First gear was spinning, but I guess wheel hopping? Tires were like "chirp chirp chirp chirp". Second gear screeched, and third gear took off. Gets to 100mph faster, but to be honest I'd rather have my original open 3.06 setup back in. I might end up swapping the Getrag gears for 3.55's sometime soon. Overall, not impressed.

I might just switch my Diablo 93 tune back to the factory 87 tune. The gears should make up for the difference, I really don't think the Diablo 93 tune does jack sh-t. Would turning MSD back on give me a couple more MPG with the 3.92 setup? Damn I miss the way my R/T sounded before the swap...


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So what would have impressed you? Everything you listed as dislikes should have been obvious before the swap...
 

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Discussion Starter #5
So what would have impressed you? Everything you listed as dislikes should have been obvious before the swap...

Harder acceleration for one, it's just meh... I'll let you guys know how it changes my 1/4 time. I wasn't aware the Getrag LSD differential with 226mm half shafts would produce wheel hop either, I thought that was just the open differentials having issues with that. Going from 3.42 to 4.10 in my 6 speed impressed me. Not so much in this 5 speed auto. People I talked to were pretty much like OMG it's gonna be a huge difference in the auto!! It's not that crazy


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This is good to know(about wheel hop) I am going to do the swap in the spring and my car has never had wheel hop?Im not sure if i like that but your tires are not great?1st gear must shift real fast tho??And let us know what gear you are in at the end of the 1/4 mile i think it will help that?
 

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I thought everyone knew the 1st gear in auto's is much lower than the 6-speed cars so they are already geared about the same as 6-speeds in first, combine that with torque multiplication from the converter and it will leave HARD, more gear in the rear is just wasted unless your running drag slicks to be able to get the power to the wheels, get a Getrag 3.06 unit as they don't seem to have the wine of the 3.92 units, I know mine is quiet as a church mouse!!!
 
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are you sure it was wheel hop and not just tire spin?

When wheel hop happens the rear cradle gets thrashed around you not only hear it you will feel it in the rear its like hitting train tracks a 60mph,
 

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Discussion Starter #9
are you sure it was wheel hop and not just tire spin?

When wheel hop happens the rear cradle gets thrashed around you not only hear it you will feel it in the rear its like hitting train tracks a 60mph,

Definitely not wheel hop then! I had traction control turned off, but only with the button. It was probably partially triggering traction control causing the chirping. I'll try the key trick to disable traction and ABS and see what that does.


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I'll be interested to see your 1/4 times. Hard to believe that much gear change isn't going to be noticeable.
 

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Discussion Starter #11
I'll be interested to see your 1/4 times. Hard to believe that much gear change isn't going to be noticeable.

The more I mess with it, the more I like the change. Definitely will be a 12 second car now. Has its ups and downs, but I'll really hammer it once the gears are broken in and I change the diff oil to Amsoil. Surprisingly I'm getting better gas mileage now on the highway! Thought that was super weird.


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Don't you have to enter the new gear ratio into the cars computer.? Or maybe u did that and just didn't mention it. Or is that just for tire size?
 

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Discussion Starter #14
Don't you have to enter the new gear ratio into the cars computer.? Or maybe u did that and just didn't mention it. Or is that just for tire size?

Yup, changed it the same day. I noticed it wouldn't even shift out of first, and wouldn't allow me to shift into manual mode without calibrating for 3.92 gears. Tire size was still saved on the tuner.


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Discussion Starter #16
What kind of difference did it make on your 0-60 time?

I've only tried it once with the 3.92's, but I'm still getting the same 0-60 as the 3.06's, 4.8 seconds but that's because of traction issues haha if I could get traction it would be a totally different story. I'll try starting out in 2nd gear next time for the hell of it.


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Doesn't surprise me a bit. I want to mod but am hesitant because I believe the engineers already determined the "pros and cons" when they settled on final design. I realize that any mods I will do will come at a cost. That is why the Hellcat may be my next car. They built a streetable race car. Oftentimes modded cars are fast but not good at slow speeds.


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