Digging Myself a Hole - 2013 Genesis 5.0 R-Spec 4.18 Coupe Final Drive w/ LSD Swap

[lyricalvanity]

Before I get to the meat and potatoes of the issue, I'd like to familiarize anyone reading with my journey so far. I owned a 2009 3.8L Sedan from 2014 through 2020. I loved the car to death and got it up to about 280k miles before passing it on, still running beautifully, to my younger brother. I passed it on because in November of 2020 I finally got the opportunity to pick up a 2013 5.0 R-Spec. Maybe I have modest goals or dreams or however you want to put it, but this has been my dream car. I'm crazy about this car and I knew for years before I bought it that I was going to exhaust EVERY option for getting the most performance and the best driving experience I possibly could from it.

I started with the template established, from my perspective, by Xtalgic on Youtube. Coupe Brembo brake swap and 2018 G80 Sport wheel swap. Next, I got the BC Racing coilovers and the ECU and TCU tunes from 10fintec. Then, I stumbled on a thread here in the forums where tonfinnhead talked about swapping in the 4.18 differential from a coupe to his 5.0 R-Spec.

Hey guys. Long story short the diffs swap without any issues. I'm running a 4.18 from a 2.0 coupe in my 5.0 r-spec. Just switch to the 3.8 sedan axles and you are fine. No tuning needed. The computer goes by rpm and speed to calculate shifts. Heres my gen running an e85 blend with the 4.18 diff. Look at which gear it kicks down to. Usually you do not see 5th until about 120

I immediately started doing my research with the intent of getting this swap done. So far, I understand the splines are different for the 4.18 differential, requiring the 3.8 Lambda axles. What I have not been able to nail down is whether or not 2. 0 Coupes were sold with both the 4.18 differential AND the Torsen LSD. From what I've found so far, it looks like this is not the case, which leaves me with two options; buy a 4.18 diff and install an LSD sourced either from another 3.727 diff or from Quaithe, or get a 3.727 diff with the LSD and install new 4.18 ring and pinion gears.

Can anyone help advise on which of these avenues is best? As we all know by now, the 5.0 R-Spec does not have a mechanical LSD, instead utilizing an "electronic LSD" actuated by the ESC system's manipulation of the rear brakes when wheel spin is detected. I'm over that, very much want that mechanical goodness.

In addition to the differential and LSD swap, I found ATQ Automotive in Ontario who have aluminum/polyurethane differential bushing kits for both the Coupe and Sedan models. Check them out if you're looking for a more surefooted acceleration profile. They also produce subframe bolt rigid collars.

Thanks for taking a look, everyone. I'll have updates out to you as my parts arrive and are installed.

 

[Jorion23]

Keep me updated. I just got a 5.0 R spec and just cant believe it cant push out more power.

 

[lyricalvanity]

Keep me updated. I just got a 5.0 R spec and just cant believe it cant push out more power.

Will do. I'm awaiting delivery for the majority of the parts as of now. I plan to update this thread with pictures of the installs and of course the final product.

 

[MG8]

4.18 gears kick ass!

 

[Steve2020]

Mechanical limited slip would be fun, it should have been an option on all of them. I'd be a little worried about it though with the weight of these cars (~4300 lbs/1950 kg) and the size of the axles, ring and pinion, companion flange and its bolts. As long as you keep a hard tire on it you may be fine. Maybe I'm just being a Chicken Little but I thought I'd throw my 2 pennies in. I wish you the best of luck.

 

[lyricalvanity]

Mechanical limited slip would be fun, it should have been an option on all of them. I'd be a little worried about it though with the weight of these cars (~4300 lbs/1950 kg) and the size of the axles, ring and pinion, companion flange and its bolts. As long as you keep a hard tire on it you may be fine. Maybe I'm just being a Chicken Little but I thought I'd throw my 2 pennies in. I wish you the best of luck.

Thank you for the well wishes. Also, I'll keep this in mind.

Also, an update for everyone. I have all of the parts in hand except for the differential bushing kit from ATQ. Supply chain issues remain in effect, but they should be here soon. To Steve's point about the axles and gears, I've had the same fear myself and have been reevaluating that part of the build. It's possible I may decide to go completely insane acquire a third party LSD solution. I'll know more once all the parts are in and I'm in the process of taking it all apart.

Thanks to everyone for checking in on the thread.

 

[Steve2020]

Thank you for the well wishes. Also, I'll keep this in mind.

Also, an update for everyone. I have all of the parts in hand except for the differential bushing kit from ATQ. Supply chain issues remain in effect, but they should be here soon. To Steve's point about the axles and gears, I've had the same fear myself and have been reevaluating that part of the build. It's possible I may decide to go completely insane acquire a third party LSD solution. I'll know more once all the parts are in and I'm in the process of taking it all apart.

Thanks to everyone for checking in on the thread.

It's a shame they didn't just make a couple of changes to the R-Spec models and market them as a performance sedan while keeping a non R-Spec v8. You can get upgraded axles for coupe differentials and Quaife makes a non-locking LSD for the coupes for $1200 USD. I don't think I'd worry about trying to upgrade the companion flange or use stronger u-joints since you can't strengthen the transmission and you don't want that to be the weak point. Don't get me wrong I love my car, I'm just a little disappointed about some things.

 

[lyricalvanity]

It's a shame they didn't just make a couple of changes to the R-Spec models and market them as a performance sedan while keeping a non R-Spec v8. You can get upgraded axles for coupe differentials and Quaife makes a non-locking LSD for the coupes for $1200 USD. I don't think I'd worry about trying to upgrade the companion flange or use stronger u-joints since you can't strengthen the transmission and you don't want that to be the weak point. Don't get me wrong I love my car, I'm just a little disappointed about some things.

No, I understand 100%. Mine is at 105k right now, so plenty of life left to live. Once she gets a bit more up there, I'll be looking at getting a G70 3.3T to continue the tradition. Very happy to see this model is getting a lot more aftermarket support.

 

[Steve2020]

When you get your 4.18 LSD swap done and beat on it some please post how it's doing. I'm interested in doing it myself if it holds up. I've got some fairly soft tires on the back and it doesn't do too bad considering it usually pulls with one tire. This car would have a home for life with a good LSD, lol.

 

[Tonfinnhead]

I am now running toyo r888. The diff is pretty strong. I'm getting no spin launches at 2,000 rpm and she pulls hard. Best 0-60mph so far is 4.58 after being heat soaked. Both tires are engaged as long as you are going straight.

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[WhiteShadow]

Wondering how OP made out with the diff swap? Looking to pick up a 2013 R-Spec in a few weeks and it could definitely use a little more get up and go off the line.

 

[edwin.foster]

I am now running toyo r888. The diff is pretty strong. I'm getting no spin launches at 2,000 rpm and she pulls hard. Best 0-60mph so far is 4.58 after being heat soaked. Both tires are engaged as long as you are going straight.

Just wondering after a couple of years if you are happy with your differential?