Z1 Motorsports Polyurethane Motor Mounts in a 6MT Sedan
 

Ten years ago, I was having issues with my 2003 Maxima SE 6MT, trying to mitigate the infamous "3rd Gear Crunch", which was a common problem with the synchros in the 5.5 Gen Maxima’s manual transmission. Brian Catts of Cattman Performance urged me to replace the fluid-filled bushings in the motor mounts with solid polyurethane from Energy Suspension. He claimed it would reduce overall movement of the drivetrain, theoretically making shifts a lot smoother. Brian was an awesome vender to the Maxima aftermarket, and he was absolutely right… after the mount bushings swap (and long hours at the shop), that "crunch" was gone.

But man-oh-man, there was so much more! Not only were gear changes smoother, but there was significant improvement in throttle response, and a noticeable improvement to the steering. Best of all, there was a new, visceral feel to the car that just wasn’t there before. For the Maxima 6MT… Best. Mod. Ever.

Now I’m no engineer, (just a suburban garage hermit), but I still think I understand what’s going on here. It takes a fair amount of mechanical energy to lift and rock the weight of an engine. So, if you minimize that movement, some of that energy is going to transfer through the drive-train, instead of getting damped by the bushings and wasted by lifting the engine. As for the steering, I suspect steering-feel benefits by having the overall weight of the car planted and consistent.

The trade-off is obvious: increased NVH (Noise, Vibration & Harshness), something manufacturers go to great lengths to tamp down. Even though I actually like a solid suspension in a car like my G, to be honest it was really severe in the Maxima. However, everything I’ve read about the G/Z mounts (so far) leads me to suspect the NVH with poly mounts in the G/Z is less severe than what I experienced 10 years ago. At the least, it’s minimal when compared to the added NVH from using a polyurethane transmission mount. And since I already have the poly transmission mount, I’m expecting not to be overwhelmed by the changes in the way my car is set up.

But I don’t really know yet, because like most things it's all guesswork. For a few years here, I badgered 4DRZ to get these mounts first, which he eventually did, and was really positive about the mod. So there's that.

Z1 Motorsports sells poly motor mounts for $200/pair, or for $160 on Black Friday, which is what I did. The parts have been sitting in my office since last Thanksgiving. Just sitting there in a little box.

Since I've been considering this mod for something like three years, it's time to just do it. So the plan is for a mid-to-late April install, after my summer wheels & tires go back on. I’m expecting shop charges between 2-4 hours of lift time, but that’s just a guess. I know this is still a month out, but I thought to start a thread anyway, and see if there’s a conversation here.

http://www.johnclare.com/pics/cars20...tor_mounts.jpg

Id be curious to know how much NVH it actually adds. My car already seems to vibrate quite a bit even at idle and WOT towards redline. Although, at 135k my original mounts may be pretty worn by now..

There's a slight increase at idle but its not bad. Engine seemed to respond slightly quicker too. I already had the z1 poly tranny mount so it might be more noticeable if you're on the stock one. However having the front end all tightened up really lets you feel how slack the oem rear diff is.

On that note... I also have this little guy sitting in the corner, waiting for nicer weather and summer tires. Matched with the Whiteline diff bushings that have been on the car these last two years, whatever slack there may be in the rear will be tightened up, for sure. But like I said, I'm waiting for warmer weather to install, and summer tires so I can tell the difference, if any.

http://www.johnclare.com/pics/cars20...f_brace_01.jpg

4DRZ get's a second shout-out here for leading the way on this diff brace.

Subscribed to see how it goes. My 6MT sedan has so much slop for a car that is supposed to be sporty. Trans, diff, suspension. Hoping new tires/rubber quiets some of that down, but it is obvious that more is needed. And since I'm saving for a FI resonated HFC/catback setup I think NVH is the least of my worries.

On the RX7 IT-S racecars we swapped to delrin motor mounts. The stock rubber would let you move the engine by hand; the Mazda Motorsports versions would let you move it with a torque bar. The poly disintegrated due to engine heat I think. Delrin held up great but .000001 flex (vs. solid aluminum which had zero flex).
One version of upper strut bar for the FC3S platform has (had?) a tab for a torque brace that kept the engine from twisting when revving. That seemed to do much the same thing without any increase in NVH. Anyone tried that? Google is telling me no, but absence of evidence is not evidence of absence.

Yea, thats on my radar as well. Wondering how it would do on a car with oem bushings still in place. Can't be bothered to get poly until stock ****s the bed lol

I usually agree about not fixing a problem until it happens, particularly something as messy as replacing the main rear diff bushing. My original was fine, but I replaced it anyway because the car was at the shop for a gear swap, so it seemed a reasonable opportunity.

I would think using the diff brace without poly bushings would put more stress on those bolts than otherwise. But that's just a guess. Honestly, I was hoping for a flood of comments in that diff brace thread after the group buy. Instead, just a lot of crickets. Maybe because winter. :dunno:

https://www.myg37.com/forums/drivetr...ial-brace.html

I installed the diff brace last week: https://www.myg37.com/forums/build-t...ml#post4239404

Based on that positive experience, I'm even more psyched now to get these motor mounts in.

:eekdance:

Swung by the shop and met with the mechanic, to go over the install of the motor mounts. Made an appointment for two weeks from today.

Pretty excited for this mod.

:dance:

while i did motor and transmission mounts at the same time all i can say is wow.. the car is solid as a rock still getting use to the Transmission mount vibrations at a stop but once the car is moving you cant really tell its in there

You can say more than "wow". Go ahead, dish the details, Chuckie.

This happened recently?

youll be surprised how much more solid the car feels with the mounts.. definitely will put a smile on your face..

LOL... nope. The mechanic looked up labor estimates last night and kind of freaked me out.

We'll see what happens. :hsugh: I'm committed to this mod now.


8:00 AM - Just dropped the car off at the shop. :HYPER:


1:30 PM - Call from the shop, no problems, and the expectation that I get the car at the end of the day. (knock on wood) Apparently he wasn't comfortable re-using the OEM top-nut because the head is shallow and he doesn't want to round it. So he's getting new hardware. Other than that, no issues.


5:00 PM - Retrieved the car, drove all over the place, then put it in the garage just before tonight's rain. I'll bump this later with some thoughts.

Rusty OEM mounts compared to shiny new ones.

Not that it means anything at all, or that I will ever lay my eyeballs on them again, but here they are.

http://www.johnclare.com/pics/cars2019/oem_mounts.jpg

http://www.johnclare.com/pics/cars20...tor_mounts.jpg

Motor Mounts Review
 

And here's my review after first impressions.


COST

Like I said up top, I paid $160 shipped for these mounts, on a Black Friday promo. Labor costs were 4 hours at $110/hour, which is this shop’s pure labor rate when you bring your own parts. It’s kind of high, however the guy doing the work impressed me last year when I had a clutch MC problem, and he was a Nissan Tech in his previous employ. On top of that, the book estimate is 3 hours for one side, and 4 for the other… which is nuts, and exactly what an Infiniti Service Shop would have charged. Turns out he didn’t have to strictly follow all the steps the book calls for in order to swap the mounts, so his experience and skills brought this down to a 4 hour job.

Anyway, if you add it all up (plus tax), I spent $635 total on this project. Yikes! :icon09:


IMPRESSIONS

I drove around back roads for about a half hour before heading home. Turns, hills, and speeds between zero and 60. I stopped the car in the middle of the road a few times to launch, with and without TC. I think I gave it a good shake down.

There’s no added noise. However, over the last three years, the Z1 transmission mount occasionally creates a nasty resonance that you both hear and feel, and in my test-drive it felt like that experience was a little more pronounced than before. I can deal.

There’s some added vibration at idle, felt through the shifter and the steering wheel. Not much, really, and in a few days I’m sure to not even notice it. And there’s zero added harshness. The ride is unchanged in terms of comfort. And the steering feels unaffected as well, which is a shame because I was expecting something here.

Now for the good stuff… the car is, without a doubt, much more solid. I hate being so vague, but its true and the best adjective applied here. There’s no sense whatsoever that the car is rocking front to back or side to side. It’s a good feeling. Shifts are definitely easier, up and down, meaning there are always moments when a gear shift is less than perfect, and with these mounts in those moments are less frequent. I got this same impression with the diff brace. And the throttle feels more responsive, not as a sea change like my old Maxima, but noticeable and welcome nonetheless. In a strange way, the drivetrain is more smooth because it’s less sloppy. NVH be damned, this is an improvement.


CONCLUSION

Is this a worthy mod? Sure, no doubt. But is it worth $635? Well… no. :hsugh: Now that it’s done, I’d rather have that money applied to something else, like a tune. What I'll probably do is rationalize my way through this mod, because what's done is done, and it really is an incremental upgrade afterall.

You have to take into account how my car was already situated, and factor in an annual budget, in order to get to this conclusion. Someone with a high mileage G, or an automatic transmission, or an unconstrained budget, might come to a completely different opinion.

In the end, I’ve no regrets, and I have a strong appreciation for what this brings to the drive. But the cost isn’t worth it... unless you DIY the mounts. In that case then heck yeah it’s worth it, because really it's just the labor costs for the install that blow it up.

Lastly, if I were to compare this project to the Bell Raceworks Diff Brace, allowing that I did the diff brace first, then the Diff Brace wins that choice hands down.