DIY: Torque Rod/Engine Mount Mod for 6MT

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To start, the 6MT Civic LX comes from the factory with a soggy shift assembly. The engagement is neither positive nor crisp. It almost feels misaligned. When stepping on the accelerator, you can feel the engine wind up in its’ mushy mounts as the rpm’s build, and feel as the car’s drivetrain hesitates before it surges forward. Trying to power shift at high rpm’s during hard launches is hardly confidence-inspiring as the excessive wheel hop and driveline lash causes the traction control to go bonkers and bog the engine down. And even if you turn off the TC, you’ll just grimace as the tires squeal horribly and leave an awful skid mark in your wake, while going nowhere fast.

All done in the name of reducing Noise, Vibration, and Harshness – or maybe Honda is just cruel and doesn’t want us to have any fun :p. Of course, why else would you buy a 6MT Civic?

To remedy this, we need to get a few items from the OE parts bin and swap them out, after a small modification that is.

P/N’s you’ll need:

50890-TBA-A82 – Torque Rod $31.88

90108-TL1-G00 – Bolt 4.76

90161-T5A-000 – Bolt, Flg 4.77

Basically, we’re taking our torque rod (aka “dog-bone”) and swapping it with the torque rod from the CVT cars. The reason that the rod from the CVT-equipped cars is desirable is because the bushings are stiffer and will allow less slack in the drivetrain. However, before installing it, a modification needs to be made to the rear bushing of the rod.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_1138


Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_4376


The larger rubber bushings allow more play. (Sorry, did not take a before pic of the unmodified CVT mount.)

At this point, you can either use my method, or fill the mount with 3M Window-Weld, which is a polyurethane sealant that is roughly equivalent to the OE bushing’s hardness/stiffness (plenty of online tutorials for that).

For my method:

My method is different in that it uses rigid inserts that allow slight movement under light load, such as upshifting/cruising on the highway to reduce cabin vibration, but acts as a solid mount under high load by completely eliminating movement beyond a certain point. Also, silicone is utilized, primarily for its vibration dampening properties, to allow a stiffer mount without experiencing the added NVH typically associated with this type of modification.

Tools you need:

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_8345


Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_9433


Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_0162


Not pictured: basic socket set, 1/8" steel sheet, 1/2" UHMWPE rod, cutting tools

To begin, cut two pieces of polyethylene rod about 2” long and ½” wide. Then, cut two 2” strips of 1/8” thick steel, with the first being 1” wide and the second 3/8” wide. These will be your four inserts that you will press into the bushing. If you don’t have these materials, you can use any type of rigid material that will fit in the respective voids of the bushing. High strength polymer/metal is strongly recommended though.

Next, wrap the inserts with F4 silicone tape, not so tight that it is difficult to tap them in, but enough to create a tension fit. This is point where you “tune” your mount – adding more silicone tape will increase the pre-tension on the mount and reduce travel while less will give the mount a more forgiving feel. Once you have fine-tuned the inserts, coat them with a plastic adhesive and tap them in; if you don’t want to buy the stuff I used, Loc-Tite Extreme, or any generic plastic adhesive, will work.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_3137


Allow the adhesive to cure, then apply standard silicone sealant to remaining voids in the mount. After that has cured, install the mount.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_4790


To Install:

Jack the front of the car up or put it up on ramps and chock the rear wheels. Then remove the aluminum splash shield fasteners with a screw driver and lower it. You’ll see the torque rod between the rear subframe and the transmission.

When you go to remove the bolts, the first one that is connected to the transmission side of the rod is 19mm, but you’ll need to use a ¾” open end wrench to access it. The other bolt on the subframe is 17mm and is best accessed by cutting a small notch in the plastic part of the splash shield that covers it.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_0161


Remove the vertical subframe bolt first, then the horizontal one that goes through the bracket. After a slight pull forward, it should drop right out. Installation is the reverse of removal. I torqued the bolts to 30 ft/lbs and used blue loc-tite thread locker, but 'good-n-tight' should be enough.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT IMG_0160


After driving it for about 50 miles, I can say that in terms of NVH, it is like stock, except when letting the clutch out in reverse, where there is some noticeable vibration from the drivetrain. Otherwise, performance is noticeably improved under all conditions.

However, the mushy, oil-filled engine mount is still a culprit. That one is next.

Stay tuned...
 

Design

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Nice work man. How's the NVH with the AC engaged? The solid mount was annoying on the MS3 and eventually swapped out in favor of inserts.
 
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DarkLight

DarkLight

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Nice work man. How's the NVH with the AC engaged? The solid mount was annoying on the MS3 and eventually swapped out in favor of inserts.
If you were a passenger in my car, you would not notice it unless I told you what was done, with the exception of engaging the clutch abruptly in reverse or 1st gear without throttle input. Even then, giving it a little gas eliminates that momentary engagement vibration. There is no noticeable difference when the A/C is on, compared to the old mount, even with lights and stereo on while charging my phone in stop and go traffic in south LA heat. There are no body panels rattling, and the floor pan doesn't rattle either.

I have had several passengers in the car with me since installation and none of them have noticed it.

I think if I had used poly, it would be a different story. I got the inspiration to do this when I was researching the Fluidampr, and I figured if silicone dampens bad crankshaft harmonics, then it would certainly work in the engine mounts as well. The problem though, is silicone is too soft on its own, so I thought up the idea to use rigid inserts in conjunction with the silicone for the best daily driven solution possible.

So far it's working, but I am curious to see how well it holds up after 10K+ miles.

Also, for you or anyone thinking about doing this, I would recommend installing it in the car and driving it around a little bit before bonding the inserts with adhesive, that way you can make adjustments before it becomes permanent.
 
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DarkLight

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Just to update this, I've gotten around to to completing both the engine and transmission mounts, since I have the car apart for another ongoing project.

Basically, the premise of modifying the engine/trans mounts is the same as what was done to the dogbone. I fabbed up some spacers out of some old brass bar stock that I had lying around, wrapped them in the F4 tape, and tapped them in (not pictured). It was trial and error, since I did it with the mounts still in the car, so I can't really give any exact measurements.

It will be necessary to remove the airbox and battery tray from the car to have enough room to reach the transmission side mount.

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT ima


Here's the result:

Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT ima


Honda Civic 10th gen DIY: Torque Rod/Engine Mount Mod for 6MT ima


I used Permatex ultra grey "maximum torque" to fill in the voids after installing the inserts.

I'll update after I've had a chance to drive it. Curing time is about 3-4 days, due to the large amount of RTV that is needed.

ETA: https://www.amazon.com/Permatex-821...76239083&sr=8-3&keywords=Permatex+high+torque

I used 2 13 oz tubes worth for both mounts. I paid about $35 for 2 tubes locally.
 
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