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Old 02-20-2013, 11:24 AM   #1
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3.73 vs 3.55

Alright, I am buying some Roush Axle Backs at the end of the week and will be switching my 3.90s (were in the car when I bought it) to something a little less whiny. I want something that's going to give me a little bit of an edge but not so much that I have to be in 6th gear at 2,500 RPM's at 65 mph. I am leaning toward 7.73 strongly, but not if they are going to drone. I am aware of 3.55's but don't really know much about them. My real focus on this is to have my mean sounding exhaust, my strong launch and better gas mileage without the annoying drone from exhaust and whine from gears.

Help me out here guys, my wife's already told me that whatever I buy, I'm stuck with.
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Old 02-20-2013, 11:26 AM   #2
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i have 3.73 and flowmaster outlaws. i learned how to control the drone
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Old 02-20-2013, 11:27 AM   #3
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Originally Posted by Defiant 5.0 View Post
Alright, I am buying some Roush Axle Backs at the end of the week and will be switching my 3.90s (were in the car when I bought it) to something a little less whiny. I want something that's going to give me a little bit of an edge but not so much that I have to be in 6th gear at 2,500 RPM's at 65 mph. I am leaning toward 7.73 strongly, but not if they are going to drone. I am aware of 3.55's but don't really know much about them. My real focus on this is to have my mean sounding exhaust, my strong launch and better gas mileage without the annoying drone from exhaust and whine from gears.

Help me out here guys, my wife's already told me that whatever I buy, I'm stuck with.
I have the 3.73s and at 65 I'm cranking about 2000. I love the gears I wouldn't ever get rid of them. If you want better mileage get the 3.55s
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Old 02-20-2013, 11:31 AM   #4
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I had Outlaws but got rid of them because the drone was so bad. Granted, that was with my 3.90s.
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Old 02-20-2013, 11:38 AM   #5
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I have the 3.73s and at 65 I'm cranking about 2000. I love the gears I wouldn't ever get rid of them. If you want better mileage get the 3.55s
The gas mileage, I would imagine, isn't that bad with the 3.73s. My main concern, though, is the noise. I am really just concerned with the combo of 3.73 + Roush Axle Back = Drone. I really do want the 3.73s, I just don't want to be stuck with the noise. She's my DD after all.
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Old 02-20-2013, 11:42 AM   #6
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The gas mileage, I would imagine, isn't that bad with the 3.73s. My main concern, though, is the noise. I am really just concerned with the combo of 3.73 + Roush Axle Back = Drone. I really do want the 3.73s, I just don't want to be stuck with the noise. She's my DD after all.
its awful
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Old 02-20-2013, 11:48 AM   #7
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its awful
Is it worse than it would be with 3.90s? That's what I have to deal with now.

Btw Bushguts, your car's quite lovely.
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Old 02-20-2013, 11:57 AM   #8
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Is it worse than it would be with 3.90s? That's what I have to deal with now.

Btw Bushguts, your car's quite lovely.
thanks, i avg 13-14 mpgs
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Old 02-20-2013, 12:24 PM   #9
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I changed from 3.55s to 3.73s and saw little to no difference in mpg. I love the 3.73s. Best all around gear. I average 17-19mpg consistently. I have seen as high as 26.5mpg on the highway. Good luck!
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Old 02-20-2013, 12:46 PM   #10
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I now have 73s and I have no drone .I play the radio at normal volume I barly hear my exhaust untill I down shift
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Old 02-20-2013, 12:52 PM   #11
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Alright, you talked me into it. Roush and 3.73s it is.
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Old 02-20-2013, 12:52 PM   #12
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I have 3.73 with o/r xpipe and pypes super system and at cruising speed in 6th I can barely hear it.
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Old 02-20-2013, 01:05 PM   #13
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its awful
No it's not... I get like 20-21 on the high way and 17 around town
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Old 02-20-2013, 01:10 PM   #14
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I have 3.73 with o/r xpipe and pypes super system and at cruising speed in 6th I can barely hear it.
Beautiful car, bro.

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No it's not... I get like 20-21 on the high way and 17 around town
That's what I thought. The gears I have now are steeper than 73s and I somehow manage to get decent mileage still. It has to get better lol.
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Old 02-20-2013, 01:25 PM   #15
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Beautiful car, bro.

That's what I thought. The gears I have now are steeper than 73s and I somehow manage to get decent mileage still. It has to get better lol.
Thanks man
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Old 02-20-2013, 03:36 PM   #16
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As long as you don't go FI 373s but I have 331s and I love them for my application!
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Old 02-20-2013, 03:44 PM   #17
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5LHO is just getting started.
Whine from gears is setup error, period. 8.8s are notorious for whines with steep gears but, that's because of the slap-dash setup on the factory line.

A shop that properly patterns the gears on load and decel should have no issues with whines.

The way Ford does it is slap the gears in and bang the pinion nut to a specified torque, job done. A crush sleeve sets up the backlash. This is no biggie with 2.73 gears but can introduce enough error for steep gears to whine.

I patterned mine when I pulled the cover to change the fluid and yep, pinion is too deep, according to my measurement. Hence the slight whine in a narrow speed range on the highway.
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Old 02-20-2013, 04:09 PM   #18
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Totaly agree, noise or drone = bad install.
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Old 02-20-2013, 04:16 PM   #19
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Roush with stock cats has zero drone.

With O/R X or H is another story. If that is a plan for the future, 100% recommend Borla S-Types as there is zero drone with O/R X.
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Old 02-20-2013, 04:19 PM   #20
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5LHO is just getting started.
Just to be clear, drone from the mufflers can't be cured without other muffs but, gear noise is install fail. Setting up 8.8s is a PITA, because of their design but, take your time and do it right and it can go well.

I find it pretty annoying that Ford hasn't figured out an answer to this, despite having 8.8s in vehicles since 1983.
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Old 02-20-2013, 04:20 PM   #21
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Quote:
Originally Posted by Defiant 5.0 View Post
Alright, I am buying some Roush Axle Backs at the end of the week and will be switching my 3.90s (were in the car when I bought it) to something a little less whiny. I want something that's going to give me a little bit of an edge but not so much that I have to be in 6th gear at 2,500 RPM's at 65 mph. I am leaning toward 7.73 strongly, but not if they are going to drone. I am aware of 3.55's but don't really know much about them. My real focus on this is to have my mean sounding exhaust, my strong launch and better gas mileage without the annoying drone from exhaust and whine from gears.

Help me out here guys, my wife's already told me that whatever I buy, I'm stuck with.
It's called dynamat
Put a little in your trunk
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Old 02-20-2013, 10:13 PM   #22
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Here is my Roush exhaust.

http://youtu.be/KYbkxmx__v4
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Old 02-20-2013, 10:45 PM   #23
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I have the Roush Axleback and they are awesome. I have the stock 3.31 gears and the only time there is even any hint of drone is at very low RPM under 1K in the upper gears 4,5,6 while accelerating. Cursing on the highway in 5th of 6th between 1500 and 2500 there is NO drone so gears should not effect the drone at all. If i had to do it again though based on what i have read here I would have bit the bullet and bought Borla S-type as I plan on doing an O/R H or X pipe. From what people have said this Roush+O/R results in ears bleeding. Something to think about if this is what you plan on doing. Just like nosypmpathy said.
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Old 02-21-2013, 01:15 AM   #24
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I have 3.73's with roush axelbacks. They have no drone and are pretty smooth at cruising speeds. I'd say about 3000 is when u really hear it. Music to my ears. My gas is not bad even at 93 I'd say go with 3.73 specially if ur looking for that extra edge
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