3.8 V6/3.3T rear differential on a 5.0 Genesis

carguy75

Registered Member
502
148
43
Atlanta, Georgia
Genesis Model Type
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
502
148
43
Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)

carguy75

Registered Member
502
148
43
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

SUPPORTING MEMBER
151
43
28
Louisiana
Genesis Model Type
2G Genesis Sedan (2015-2016)
Probably the bigger thing to hope for is that a dealership is capable of altering gear ratios without replacing large chunks of feature programming.
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EdP

Supporting Member
SUPPORTING MEMBER
SUSTAINING MEMBER
3,705
911
113
Parrish, FL
Genesis Model Type
Genesis G80
Probably the bigger thing to hope for is that a dealership is capable of altering gear ratios without replacing large chunks of feature programming.
Good point. It was easy to change gear ratio when all you had to do was watch the tach and shift. I wonder how it changes how the transmission as well as other parts of the system work with the computer.
 

carguy75

Registered Member
502
148
43
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

Hasn't posted much yet...
40
6
8
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

Hasn't posted much yet...
40
6
8
Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
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

Registered Member
502
148
43
Atlanta, Georgia
Genesis Model Type
2G Genesis Sedan (2015-2016)
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

Been here awhile...
150
11
18
Md
Genesis Model Type
1G Genesis Sedan (2009-2014)
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

Hasn't posted much yet...
40
6
8
Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
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

Registered Member
3,158
12
38
Minnesota
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

Been here awhile...
150
11
18
Md
Genesis Model Type
1G Genesis Sedan (2009-2014)
I believe some of the early 4.6s did have a mechanical non electronic L/S. Tailwalker may know for sure.
 
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