In the Rear With the Gear

"Methylsulfonylmethane" (methylsulfonylmethane) 05/28/2019 at 13:15 • Filed to: Project Hoondy

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While all of Project Hoondy’s modifications have involved a long planning phase, the rear end rebuild really tried our patience. The sheer !!!error: Indecipherable SUB-paragraph formatting!!! involved as well as complications in getting a swaybar to fit on our new rear subframe delayed the build to previously unseen levels. What we hoped would take a couple of months ended up dragging on for more than a year.

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Part of the reason is that we actually had to abort the mission when the build was at a less ambitious phase. We’d originally planned to slap the 4.18 gear set and carbon fiber driveshaft into the car by themselves with our buddy Andy’s help. This was before the rear end developed its wandering issue. We were defeated by the bolts that held the lower control arms onto the subframe, we just couldn’t get them loose for the life of us. Since we had planned (rather foolishly) to re-use all the control arms and hardware we were unwilling to remove anything destructively.

We also discovered that our driveshaft didn’t fit. Driveshaft shop had sent us the wrong unit, possibly the one they make for the 2.0 liter turbo version of the Genesis coupe. Either way, we weren’t able to install any of our new parts on that occasion. We arranged to have the driveshaft replaced and made a plan to return to the build.

Shortly thereafter, we attended a drift event which is probably what provoked the rear end problems that developed almost immediately afterwards. That’s when we decided to get more ambitious with the build by adding the subframe swap and full control arm replacement. This added considerable expense to the build, which delayed us further as we acquired all the parts.

But finally, at long last, it was time.

To say that the scope of this build had outgrown our ability to complete it on our own would be a massive understatement. After the fiasco that was our first attempt, Andy was unwilling to help us make another go of it and we certainly couldn’t blame him.

Happily, at this point the car was living in the Denver area and there are many excellent mechanics local to it. The grassroots drifting scene there is strong and there are several shops that feed it. While many of them are good, one in particular stood out to us early on.

After Hours Autosports is a small shop located in Golden Colorado. Started as a one-man, two-lift operation, it is headed up by the talented Mr. Justin Chestnut, often supported by his cool-ass father Bob. Though small in size, After Hours has turned out some killer builds. They run the full gamut from regular maintenance to full-on drift machines. European, Japanese, and Domestic, they do it all; though over the years they have come to specialize in BMWs due to Justin’s own E46 drift car.

Suffice to say, they were more than well-equipped to take on our project. Though, despite their high level of expertise, they offer very good value for money as well. By keeping their operation lean, they offer one of the lowest shop rates in the area while still turning out top-quality work. They even proved this out to us when we had an unexpected fuel pump failure on Project Hoondy. Justin had us sorted out and back on the road in just a couple of days for much less money than we’d been quoted by a local “import specialist” shop. After hours earned our repeat business and then some, making us excited to bring the car back for our massive rear-end build.

While we were daunted by the scope that the build had grown to, this sort of thing is absolutely routine for Justin and his crew. Rear end swaps, upgrades, and rebuilds are some of the most common procedures in the drift world; such as this tasty rear end refresh done for an S13 earlier in the year:

Once they had their hands on Project Hoondy, the build went by in a blizzard of mechanical action. Out with the old:

...and in with the new:

The sedan subframe truly is drastically beefier than the Coupe unit, which itself is already quite heavy-duty in nature. Compared to the delicate little S13 subframe above, the Genesis Sedan assembly is humongous. Massive hydroformed legs, chunky reinforcing straps, coffee-can sized body bushings, it looks more like it belongs on an SUV than a sleek sports car. While the weight penalty isn’t the most performance-oriented feature imaginable, the sheer strength of this assembly lends itself well to the rough-and-tumble world of drifting and hard driving.

After Hours made the install look easy, even when we were thrown another curve-ball from Driveshaft Shop. It turned out the replacement driveshaft they sent us was also too short. We were furious, it was a big enough cock-up the first time, but making the same error twice in a row just speaks to a level of carelessness that says nothing good about their attitude towards customer service.

Luckily, After Hours had both enough experience with Driveshaft Shop and driveshaft modification know-how to take the problem in stride. After a stern talking to over the phone, Driveshaft Shop rush-shipped a custom adapter plate that arrived the next day.

At roughly half an inch thicker than the standard plate, this new adapter took up the extra length that the driveshaft was short by without us having to go through the three-week agony that was the return process we experienced the first time.

While Driveshaft Shop deserves at least some credit for finally getting their shit together on this project, we mostly give props to After Hours for identifying the problem early on and organizing such a quick solution. Most shops would have thrown their hands in the air and left it up to us to deal with Driveshaft Shop and their protracted RMA process.

Bob also found that our fancy new driveshaft interfered with the OEM stainless steel exhaust heat reflector. Unwilling to do away with it (especially given the increased heat sensitivity of a carbon fiber driveshaft over the OEM steel unit) Bob carefully trimmed and massaged the heat shield and reinstalled it, doing such fine work that it is virtually impossible to spot the modification.

With the driveshaft fiasco out of the way, it was smooth sailing from there.

Nobody makes a performance after-market replacement for the rear lower suspension arms, so we settled for some standard pattern parts from Moog. We attached them to the subframe with an ISR eccentric lockout kit. The OEM setup uses bolts set in eccentric washers that are twisted in place to set the rear camber and toe adjustment. These fasteners are prone to slipping under heavy load, thus ruining the alignment. We could now set camber and toe with our adjustable rear arms, rendering the eccentrics redundant. The lockout kit eliminates them for a stronger installation.

We also replaced the rest of the hardware. OEM hardware is expensive and you can’t actually buy all of it individually which is an annoying, though seemingly standard practice for Hyundai.

Happily, BelMetric.com came to our rescue with top-quality automotive grade 10.9 fine-thread metric bolts with through-hardened washers and extra-stout nylock nuts. This hardware is easily as strong and corrosion resistant as the OEM parts and more resistant to loosening over time due to the added security of the lock-nuts.

And with that, Project Hoondy was back on the ground once more. It wasn’t a quick process, or cheap. How not cheap? Well...

Sedan Rear Subframe: $280 shipped

Two tubes of 3M Window Weld: $40 shipped

4.181 Genesis Coupe Differential: $250 shipped

ARP ring gear bolts: $85 shipped

Driveshaft Shop CF driveshaft: $1215 shipped

InsaneShafts rear axle shafts: $700 shipped

ISR rear control arms: $705 shipped

ISR eccentric lock-out kit: $80 shipped

Moog rear lower control arms: $230 shipped

Grade 10.9 hardware: $60 shipped

Whiteline rear swaybar kit: $185 shipped

Whiteline adjustable rear swaybar end links: $115 shipped

Expert labor from After Hours: $997.50

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Granted, the cost of parts was spread out over the course of a year, but still, that hurts no matter how you slice it. We’d argue that the car was due for replacement rear control arms anyway, which would have cost somewhere between 700 and 900 dollars in OEM parts and shop time. Even taking that out of the equation, that leaves us with four grand worth of added cost that was purely optional on our part.

Needless to say, expectations were high for just what a difference all this mechanical love would make to the car’s driving dynamics. Tune in !!!error: Indecipherable SUB-paragraph formatting!!! to get the dirt on our results here on Project Hoondy!

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HondoyotaE38: A Japanese and German Collab...wait a minute > Methylsulfonylmethane 05/28/2019 at 13:27

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LongbowMkII > Methylsulfonylmethane 05/28/2019 at 13:39

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I guess if you’ve got to add weight low and towards the back is where you want it on an FR car

Methylsulfonylmethane > HondoyotaE38: A Japanese and German Collab...wait a minute 05/28/2019 at 17:24

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You must be too young to get the Full Metal Jacket reference, but memes are fun too :D 

Methylsulfonylmethane > LongbowMkII 05/28/2019 at 17:27

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Indeed, plus weight gain from the subrame was just about entirely offset by the weight difference between the old and new driveshaft. The OEM unit is unbelievably heavy. We’ll trade body mass for rotating mass any day of the week. 

Fairlyuseless > Methylsulfonylmethane 10/02/2019 at 00:26

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Do you know if the issues that you have had are consistent in the 2013 - 2016 generation 3.8? Or are the two generations vastly different besides just the motor (and power output)?

Methylsulfonylmethane > Fairlyuseless 10/02/2019 at 02:21

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You’ll have to be more specific about what issues you’re talking about exactly.

That said, BK1 (2010-2012) cars and BK2 (2013+) cars are quite similar aside from their engines. BK2 cars have problems with excessively weak drivetrain mounts just like the BK1 (engine, transmission, and differential mounts are all far too soft and weak for sustained hard driving).

BK2 also has the heavy, weak two-piece driveshaft and heavy, weak dual mass flywheel. Both components are stupidly overweight. They slow down shifts and just suck a lot of joy out of using the engine as well as providing weak links for drivetrain shock loads. BK2 diffs are the same as BK1 (open diff or lame Torsion LSD). BK2 steering rack is a bit better, quicker ratio and feels better. BK2 manual transmissions are significantly better with carbon synchros and stronger construction. You can still destroy them pretty easily if you drive hard on the OEM drivetrain mounts though (those mounts are really the key weakness of the GenCoupe platform).

BK2 rear subframe has the same weaknesses as BK1. Sedan rear subframe swap benefits both cars equally. Brakes are the same, shocks/springs/suspension close enough to the same (early BK1 cars had a specific front swaybar end link).

We really make the OEM Genesis Coupe sound like trash with all our complaints, but we would have at least as many complaints about any other car from that segment. 350z/370z, Mustang, Camaro, FRS, BMW 325, S2000, all of those cars are similar in price and sportiness to a GenCoupe and none of them can hold up to sustained hard driving without plenty of modifications. They are all street cars, they all have heavily compromised driving dynamics as a result.

The way we see it, the only glaring issue with the Genesis Coupe is those drivetrain mounts. Everything else is similar or better than other comparable cars in its segment. All such machines need plenty of upgrades to reliably handle the sort of abuse we personally enjoy subjecting fast cars to.

As a result, Project Hoondy as it stands today is a very coarse, aggressive car to drive. Many people, even people who like fast cars, would say that it is too rough for regular street driving . Keep this in mind if you’re going to take our advice on how to build out these cars. If you aren’t looking for a manual trans rear wheel drive vehicle that you can brutally clutch-kick, drift, power-shift, panic-stop, drag-launch, and just generally beat the crap out of on a daily basis then you do not need to be as hard-core with your modifications as we’ve been. If that -is- what you want, then no new vehicle sold for less than $60 K will meet your needs. Even something like a brand new Corvette Stingray can be beaten into submission pretty easily (just look at owners who have taken them to track days).

The only way to do it for decently cheap is to build a car out like Project Hoondy. It has a 300 horsepower engine, but the rest of the drivetrain could handle 500+ horsepower no problem. Over-building like that is the only surefire way to get great reliability when you beat the hell out of your car all the time .

Fairlyuseless > Methylsulfonylmethane 10/02/2019 at 17:48

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I am actually in exactly that position. I acquired a 2016 3.8 ultimate, and have felt the drivetrain mounts issues with only mildly spirited driving. I have aspirations of improving the weaknesses so that I can take it to some track days at Laguna Seca. I have loved the build that you guys have done so far, and look forward to the next installation

Methylsulfonylmethane > Fairlyuseless 10/03/2019 at 23:27

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Ooo, lovely little acquisition you got there!

Before I get started, here’s an easy must-have for your car :

This is by far, hands down, the best fluid for the GenCoupe manual transmission. I don’t think that we’ve ever actually covered it on Project Hoondy. (We   really need to do a fluid update.) This stuff is absolutely aces, better than Redline, Royal Purple, and all the rest. It has long been known in the hot Honda community as a golden magical elixir for many of their shit-tacular manny tranny woes. It does every bit as much good in the GenCoupe and we love it to bits. You can also goose it by adding one ounce of Oil Extreme Concentrate per quart for maximum protection of your synchros and gear mesh .

Anyway!

The BK2 has plenty of advantages over the BK1, but one unfortunate disadvantage is that the drivetrain mounts are more difficult to fix due to deficiencies in the performance after-market (last I checked, anyway).

There are no options for engine mounts on the BK2. OEM is all you can get. They are pretty simple to modify though. You can use the same trick we did with our sedan subframe bushings: fill all the voids in the rubber mount with 3M Window Weld. It is trickier with engine mounts with poor access to the inner void through holes in the outer metal shell. With a little care and patience though, you can pack them nice and full of urethane. The specific packaging of Window Weld really helps here. You can cut the tip off small and at a sharp angle, then use the pointed end to really cram the goop in there.

Aside from engine mounts BK1 and BK2 are the same. The Megan Racing transmission mount works perfectly well off the shelf, though if you are making your own engine mounts you should fill the trans mount with Window Weld as well for a bit more oomph.

As for the differential situation I would recommend doing it either the simplest way (hack a second OEM mount into your OEM subframe) or the most elaborate way (full blown sedan rear subframe swap). That said, I would recommend doing the first option the right way by welding a proper sleeve into the enlarged 4th diff mount hole. Again, I would fill any OEM bushings involved in the process with Window Weld.

All the other options are just paying more money for a solution that isn’t as good. That goes double for this crazy-ass thing:

I’m actually a big fan of ATQ’s products, but this thing is dumb as hell. For the $625(!!!) that it costs you could buy a sedan rear subframe along with a beefy after-market swaybar and adjustable end-links.

Keep it simple with an OEM mount hack, go big with a full subframe swap, or go home. The aftermarket options for diff mounts just aren’t a good value, and that’s coming from a team that has spent a shitload of money on after-market parts for this platform.

Speaking of bad value:

These goddamn things.

GenCoupe g uys love the “engine leash” and sing their praises, but the fact that they make such an improvement is just evidence of how hideously awful the GenCoupe’s drivetrain mounts actually are. To be abundantly clear: t his is not a solution, this is a band-aid. It does not address the core issue that causes the problem. This modification puts a lot of pre-load force on what have already been established as weak-ass engine mounts. You don’t need a doctorate in mechanical engineering to figure out that’s gonna make those pathetic mounts wear out even faster than they already do.

Skip that shit, do it right, or at least a better kind of wrong. I’d rather try to urethane-fill OEM engine mounts while they’re still on the car than pay $40 for a loop of steel cable I wouldn’t even use to tie my dog out in the yard.

Rant over.

Glad you’ve enjoyed the series so far and we do have more to come soon. We’ve got a write-up on a small, blessedly inexpensive front axle upgrade that made a huge improvement to Project Hoondy. We’re also going to finally upgrade our brakes. We’ve already got a full set of calipers and will be acquiring the rest of the parts over the next few months as we can afford it.

That aforementioned fluid update really needs to happen and we might also do something cute to celebrate the fact that Project Hoondy is no longer an only car. An adopted older sibling has joined the fleet so now our GenCoupe can be taken out of commission without any worries about transportation to work and all the rest.

In the mean time, feel free to pick our brain anywhere in the Project Hoondy comments section.

Stay tuned!

Fairlyuseless > Methylsulfonylmethane 10/04/2019 at 03:13

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Truly, having your responses is better than having access to Mazda engineers! Not tongue-in-cheek, you already answered questions I was going to ask: thoughts on the sedan subframe swap (I really look forward to going that route). While there are some great contributors to the gencoupe forum, there is also a lot of NA to wade through.

Look forward to the next segment in the build

Methylsulfonylmethane > Fairlyuseless 10/04/2019 at 03:39

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Nice! Yea, that about covers my thoughts on the rear subframe situation. Just remember that there’s still no bolt-on solution for getting a GenCoupe swaybar to work on the Sedan rear subframe. That still requires some custom fab, but it is eeeeeasy custom fab. We were all worried about it when we went through with the swap ourselves, but holy crap is it not a big deal.

The exact placement of the swaybar just isn’t critical as long as you use adjustable end-links (which you should anyway). Get it within 3/4 inch or so of the factory placement and you’re fine. Other than that, just make sure you use heavy steel plates and a decent TIG welder to extend the subframe-side swaybar mounts. W e used 3/8 inch carbon steel plate . A higher grade of steel like Chromoly in that same thickness would be ideal, but the plates are so short that there’s not much leverage available for them to get bent with. 

If you aren’t comfortable with or equipped to do the fab yourself, just about any machine shop could handle it easily, especially if you show them photos of our own custom swaybar m ount. Four bolts, a couple quick welds, done. 

Happy tuning!