3.8 V6/3.3T rear differential on a 5.0 Genesis

carguy75

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Atlanta, Georgia
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2G Genesis Sedan (2015-2016)
I have been considering swapping the 3.73 rear axle on my 2015 5.0 for an 3.92 rear axle off a 3.8 or 3.3T for better off the line performance. Has anyone else tried swapping the rear axles from the the 3.8/3.3T onto the 5.0 models?

I have found a few used 3.8 Genesis differentials that are fairly cheap online, but not too sure of the fitment or size.
 
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carguy75

Registered Member
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Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)

carguy75

Registered Member
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275
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Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)
No reply or answer to question yet. Darn it, if this was a Camaro or Mustang I have had about 100 replies by now on what axle ratio was the best and the claimed results for using either as well as axle sizes.:)

Darn, I may have to just take a risk and install one to see what happens. However, I may wait to see if Genesis provides a mechanical limited slip rear axle to the G80 or G70 and then make the upgrade really worth it.
 

Suburbazine

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EdP

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carguy75

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Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)
The rear differential in our cars are not computer controlled, just the average mechanical gear and pinon units. It should have no effect on the transmission or any ecu programming besides the cruising speed. The only affects would be how the power in transmitted to the rear wheels. A 3.92 ratio will product more torque at the rear axles than a 3.73 ratio differential. However, that will affect gas mileage and top speed in a negative way.

Note: Good point about how the computer will see the gear changes; it may trigger a code with the sensitive electronic nannies these cars have or the ECU may just compensate for rpm difference. Luckily the 3.73 and 3.90 gears are very close to each other so the speed change should be very minor. Realistically, a custom tune or ecu tweak may need to be done to properly set this up especially for the speedo.
 
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Ducatislave

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Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
the parts should work fine, considering Hyundai lists the exact same part number for the carrier, housing and case. But as others have said, the issue that will probably arise is computer related. More-so the TCM will probably freak out, because it is programmed to know that at a certain RPM and gear the speed being received is X, so it may interpret that as slippage or potentially try and compensate by adjusting shift firmness.
This is just educated speculation, I understand the systems but have never dealt specifically with this matter.
My interest in this thread is putting a limited slip helical differential (aftermarket) for the coupe in my sedan, should really help launch that fat ass out of corners without ESC nanny getting pissed.
 

Ducatislave

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I correct my statement, in regards to the parts fitment. I was referring to the 1st Gen sedans all having the same part numbers. I do not know on the 2nd Gen.
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carguy75

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Thanks for the feedback everyone. i decided not to waste my money by buying a 3.8 rear differential until someone makes a tuner for the 5.0 Genesis that can adjust for differential gear changes.

My Diablo sport tuner for my Escalade allows me to change the tire size and gear ratio in the ecu for any modifications made. I would need a tuner that can do the same for the Genesis to properly swap axle gear ratio.
 

Roc

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May want to look for a 2009-2010 4.6 rear end with a true limited slip differential. Should fit with no mods. Would have the source test its rotation to make sure it is a true limited slip diff. Would not affect ABS, or other nannies, but maybe would limit nanny intrusion because both wheels would be turning without one slipping much more than the other on hard acceleration. Just a thought.
 

Ducatislave

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The coupe differential is a different size internally even though the casing is the same from what I've read on here.
From reviewing the part numbers you are correct.....sorta. Allow me to explain.
In terms of the limited slip(L/S) coupe differential it may be a different carrier size, however they do not list the L/S carrier on its own, only the complete rear end.
However, in regards to the non L/S rear end that is the exact same on all the Coupes and Sedans up to 2016. They even list the compatible vehicles as follows:
18628
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18629

Feel free to fact check my results. I certainly don't want to misinform people.
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scottdk

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May want to look for a 2009-2010 4.6 rear end with a true limited slip differential. Should fit with no mods. Would have the source test its rotation to make sure it is a true limited slip diff. Would not affect ABS, or other nannies, but maybe would limit nanny intrusion because both wheels would be turning without one slipping much more than the other on hard acceleration. Just a thought.
The 1st generation Genesis did not get equipped with a mechanical LSD. I've tested the rotation, and there is an old thread on this somewhere. Hyundai calls it an electronic LSD which in tern uses the traction control. Wish the car did have LSD though, at minimum in the V8 at least.
 

Roc

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I believe some of the early 4.6s did have a mechanical non electronic L/S. Tailwalker may know for sure.
 

Roc

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Those interested in LSD for your 2012-2015 Sedans may want to google Traction Concepts. They provide LSD modification kits for your current differential so you keep your rear end ratio. Said the 2012-2015 Coupe option they have will exactly fit the Sedan. Also can take more power/torque than the 5.0 can give. It also provides a locker launch if heavy throttle is applied. Believe under $400.
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Ducatislave

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Those interested in LSD for your 2012-2015 Sedans may want to google Traction Concepts. They provide LSD modification kits for your current differential so you keep your rear end ratio. Said the 2012-2015 Coupe option they have will exactly fit the Sedan. Also can take more power/torque than the 5.0 can give. It also provides a locker launch if heavy throttle is applied. Believe under $400.
Not trying to shoot down your find, as it is a good budget option ($400 compared to $12-1500 for a new L/S differential). However, I have dealt with a remarkably similar product years ago. The issue we had back then (1998-2000), and I foresee with this Traction Concepts design is longevity. If you look at the part, it is a solid (according to their site "head treated") block of iron/steel with a few springs in the middle. There is no sacrificial surface. Most limited slip differentials have either bronze wear surfaces or some type of clutch disk that is effectively the consumable part. Back then we kept running into problems on vehicles that were either driven hard or used for heavy towing. they block would get grooves worn (ground) in it which allowed it to pivot on the pin further than intended and would jam up resulting in either 1: if the block was softer than the gears, a fully locked differential or 2: if it was harder, it would start chipping the tips of the gear teeth. Overall this was resulting in failures @ 40k-50k miles after install.
This is just what I experienced back then and noticed that this Traction Concepts product appears to be similar if not the same thing.
I cannot speak to this new products longevity, they may very well have solved that problem through better control of the heat treatment/hardening process.
 

carguy75

Registered Member
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Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)
Those interested in LSD for your 2012-2015 Sedans may want to google Traction Concepts. They provide LSD modification kits for your current differential so you keep your rear end ratio. Said the 2012-2015 Coupe option they have will exactly fit the Sedan. Also can take more power/torque than the 5.0 can give. It also provides a locker launch if heavy throttle is applied. Believe under $400.
Good find. However, I really only wanted the 3.91 gear ratio instead of my 3.73. A limited slip gear kit would be nice, but I will try to see if I can swap a complete rear axle out of a 3.3T G70 for longevity in the future. Many aftermarket add-on limited-slip kits are not known for their longevity. Good for an occasional track car, but not a daily driver. By longevity I mean at-least 100k miles, not maybe 30k miles or so.
 

carguy75

Registered Member
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275
63
Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)
Not trying to shoot down your find, as it is a good budget option ($400 compared to $12-1500 for a new L/S differential). However, I have dealt with a remarkably similar product years ago. The issue we had back then (1998-2000), and I foresee with this Traction Concepts design is longevity. If you look at the part, it is a solid (according to their site "head treated") block of iron/steel with a few springs in the middle. There is no sacrificial surface. Most limited slip differentials have either bronze wear surfaces or some type of clutch disk that is effectively the consumable part. Back then we kept running into problems on vehicles that were either driven hard or used for heavy towing. they block would get grooves worn (ground) in it which allowed it to pivot on the pin further than intended and would jam up resulting in either 1: if the block was softer than the gears, a fully locked differential or 2: if it was harder, it would start chipping the tips of the gear teeth. Overall this was resulting in failures @ 40k-50k miles after install.
This is just what I experienced back then and noticed that this Traction Concepts product appears to be similar if not the same thing.
I cannot speak to this new products longevity, they may very well have solved that problem through better control of the heat treatment/hardening process.
My thought exactly. The aftermarket LSD kits are mainly for track duty cars so the short life is fine for them, but not as an long term daily driver. However, I guess some owners can live with replacing rear axles every 50k miles or so. Not myself, I want an axle that will last over 100k miles. So I will look into finding a stock LSD rear axle from a G70 in the future.
 

Roc

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Sorry too disagree, but autocross, drag racing, hill climbs, etc., require extremely robust components. Not ones that will break after a few runs or miles. These LSD kits seem to be robust. Read the specs and responses. Can handle over 650 hp/torque, yet be just like regular LSD in day to day driving. Running autocrosses, hill climbs, street racing for 50+ years, I can attest to the strength of good aftermarket systems. As the ads state, will outlast the standard rear end. The launch control lock up feature alone would solve one of the car's inherent problems when street/strip dragging for those that want the more out of their vehicle without trying to get engine mods that will never be available. Watching this forum for a few years, I've noticed many posts about wanting more performance but only very few owners actually have been willing, though with limited success, to try to extract more performance from their 4.6 or 5.0s. Most are interested in exterior/interior appearance, wheel/tire mods, etc. Quite a difference from the Mustang, Camaro, & Dodge forums. This situation is neither bad or good, but does ensure conservative posts for the 4.6 & 5.0s. The G70 section & Kia Stinger forum appear to be more robust in searching for more street performance, aftermarket equipment, and apparently has more adventurous (maybe younger) owners who probably bought their cars with a different intent than most Genesis owners.
 
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