Solved: CD009 trans on SR20DET - Vibration at 4000rpm? (Page 3 / Post #79)
 

I just finished swapping a z33 (cd000, yeah I know...) box into my s14 with sr20det. I'm getting a crazy resonance vibration at 4000rpm in any gear, and the sound isn't localized. It sounds like its in the trunk/shell of the car. The noise does not happen when free revving the car, only under load/decel.

The z33 swap was done via the cut and shut method, with the input shaft lathed down to match the sr20 transmissions. The two halves of the transmission were located via a jig setup to run through the main journals of a spare engine. Car shifts and drives fine, I doubt it's the cut and shut itself.

I've smashed out the tunnel to ensure there is at minimum an inch of clearance everywhere around the transmission. Doesn't seem to help. Can't hear the transmission clunking into the tunnel either. Anybody know how much a transmission moves under load? The motor and transmission mounts are stock 240sx. The transmission crossmember was made by cutting the stock member and tig'ing it to angle iron.

Normally I can track these things down and fix them, but this is perplexing me. Anybody got any ideas?

what driveshaft are you using? has it been balanced?

Shaftmasters aluminum. Comes balanced from factory. The vibration is only at 4000 rpm under load regardless of vehicle speed or gear. I don't think its the driveshaft.

Have you checked to see if the trans case is coming in contact with the body anywhere? its a pretty large case so it could be shifting slightly under load and touching the body.

So it's been a month now with the 350z box. I've taken it out, bashed the ever living hell out of the tunnel and ensured I have at least 1-2 inches of clearance around the box.

Still have the vibration. Gonna loose my mind.

I spent a lot of time revving the motor (neighbours hate me) trying to figure out if its doing it only under load. I've found:

1) Vibration occurs if clutch is disengaged or engaged in neutral.
2) Vibration is worse under load.

I'm now wondering if it is either bad motor mounts, bad harmonic damper, or a bad clutch.

I have an exedy hyper single and I called exedy to ask if they can go out of balance, tech said it is unlikely and they are balanced to 15,000 RPM.

So is there a chance this could be a harmonic balancer or motor mounts? My balancer and mounts are OEM and ancient, but I can imagine they would cause a vibration this bad.

Thoughts?

for sure I'd try a new crank pulley. if its just the stock sr20 one it should be easy to come by. motor mounts are easy enough to replace, worth trying a new or different set. you aren't using a solid trans or motor mount are you?

Thanks for the replies!

Yeah, stock pulley, but I think I'll just buy an ATI Super Damper.

Currently using OEM motor and trans mounts on a motor that made 513whp, so that could be the culprit too. Gonna get a set of the megan motor mounts as the nismo ones are impossible to find. If anyone has something available that's better to recommend I'm all ears.

interesting thanks for this info

I'd try the motor mounts and tranny first. They're a lot cheaper than a ati damper. Not only that, we already know those mounts are shot.

ati super damper is dope. I have one, but the fit over the crank is STUPID tight. I took some emery cloth and hit it for a few minutes to loosen it up a bit. Its still a snug fit, but before it would have been "install one time, never be able to remove it"

also, I have a set of used nismo mounts for sale if you're interested. Good condition, (no trans mount, just engine).
Hit me up in the DM if interested.

got engine an trans avail if need all three!

So ripped the transmission out (again) last night. Was looking at the exedy clutch, and noticed that the blue paint marks for balance were off! I must have inadvertently installed the clutch out of alignment. The marks were off by one bolt hole.

Here's where it gets weird though. I called Exedy and the service rep said that the clutch being off by that much shouldn't matter. They balance the flywheel and pressure plate independantly of each other. They then put them together and mark the best balance with the blue mark, but both should be zero balanced. This makes no sense to me, as why mark the clutch at all then?

What do you guys think? Should I take the clutch to a third party shop and verify Exedy's work? Or should I just fix the balance alignment and slap it all back together?

Hey did you figure this out?

I'm having the same problem, except at ~5500 rpm.
Happens in neutral under zero load, or during a pull under load.

I think it's even being picked up as knock.....and if so I've been chasing this for a couple of years now thinking it was other things.

SR20DET trans / 6 Puck ACT HD / Fidanza Flywheel.
Driveshaftshop AL Driveshaft - but since it's happening in neutral that shouldn't matter either.

Just noticed this last night so any help would be appreciated.

You can take anything trans related past the input shaft out of the equation if it's vibrating in neutral when revving.

But don't exclude the input shaft and/or bearings though. Just to clarify what Def said.

Thanks for the input everyone.

I'm still battling this vibration issue. Since I last posted here's what I've done:

-filled motor mounts with window weld
-aligned exedy hyper single with balance marks (sent it out to shop to ensure it was balanced correct)
-ran engine without belts to rule out pulleys
-ran engine (briefly) without harmonic balancer to rule it out (holy shit that leaks a lot of oil from the front seal)

Still vibrating like crazy and my filled motor mounts are making it worse!

I even went so far as to measure the frequency of the vibration. It's occurring at 2x engine rpm. According to engineering books out there 4 cylinders should have this normal vibration as there are two spark events per crank shaft rotation. The amplitude of the vibration is way high though, which is what's driving me crazy.

Some of the books mention that a vibration at 2xRPM can be caused by two shafts being misaligned. I'm still not convinced this is my issue as it's happening with clutch pedal depressed and car in gear. Input shaft at this point should be locked and not spinning.

My next plan is gonna be to hop under the car with the motor running and run a stethoscope to the input shaft through the slave cylinder window. With the clutch in and gear engaged I should be able to tell if the input shaft is vibrating.

Okay another update. Still getting this vibration. I have since the last post done the following:

-Milled down the bellhousing to ensure it is absolutely flat
-Lathed up some offset dowel pins so I could guarantee concentricity (input shaft lines up perfectly with pilot bushing)
-Installed new pilot bushing
-Tigged up a new transmission crossmember (trying to make it stiffer, ha)

Still vibrating! Input shaft bearing is completely silent now however. It's actually amazing how silent the bearing is. This leads me to believe that the alignment of the box is now for sure not an issue.

I ran the motor with a spare sr20det transmission bellhousing installed to verify that the vibration is something to do with the z33 transmission. With the sr20det bellhousing the vibration is completely gone.

The only thing I can think of now is it has to go with engine flex. I don't notice the shifter moving when driving the thing though. My last thought before I light this car on fire is the transmission may be moving upwards under load. Theres only about 1/3 of an inch clearance in a couple places, so it must be touching the body somewhere. I'm going to try to measure the transmission's movement and see if it correlates with the amount it would have to move to hit the body.

If anyone has any other ideas I'm all ears!

Did you use a heat plate to heat up the damper prior to install? Did that for mine and it went on like a breeze!

throw some rubber over the top of the trans and see if that quiets it down. I'm wondering if the trans is contacting the sheetmetal of the body and causing it. I know mine, I had to pound the shit out of the trans tunnel, and I ground down a bunch of the useless things on the trans that stuck out (bosses for bolt holes and stuff, not the actual case)

didn't even think of that, I just used neverseize and kroil

truth on nismo mounts being impossible to find. took me over a month to get a set after I ordered them.

we have them in stock.

z33 transmission on sr20det - Vibration at 4000rpm
 

You're positive is noise of it hitting the body? I had an incident with my DP hitting my frame rail and it was diff of a noise versus my gearbox decel noise . With my sr once I put a lightened flywheel, stage 2 clutch and one piece driveshaft, I noticed I could hear more "racecar" noises from the gearbox and the diff. In gear on decel I get chattery noises from 3k down to 2.5k and I thought I did something wrong. But it's normal . I threw in a lighter flywheel and a one piece driveshaft. Remember the OE flywheel is a decent weight and the OE driveshaft is two piece. The flywheel is harder to turn when being driven by decel and the the two piece driveshaft takes gearbox noise at the split . With solid this and one piece that you're going to get more feedback that would normally not present itself . Did your clutch look chewed up when you took the trans off? Is there a lot of movement on the input shaft or tail shaft? If everything looks cherry it could be normal man. I spent a long as time googling the shit out of the internet and realized it's just normal for MY setup. The only difference is you'rs is there when in neutral? At that point it's something engine related (if your foot is on the clutch) and I've read threads about the ATI dampener causing rod bearing failure but it's hit or miss. Just my two cents


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I have Nismo mounts for sale (just engine, not Trans).

Since when did ATI Dampers cause bearing failure [emoji23]


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I think it was obvious when I said it was in threads I read dude, not my experience.


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yeah but if you're gonna post something like that, you need to support it, not just make the claim and then pass the buck. "oh i read it somewhere" doesn't do much to support your statement.

I didn't mean it as in "this is what's happening" I should've made it more clear I meant in the sense of after changing out to after market parts and trans swap he has this noise now. He should go back to OEM if he can't pinpoint where it's coming from. He states that putting the sr trans back made the noise disappear but he hears it with his foot on the clutch too. That points engine related, so it's kinda weird unless there's an alignment issue with the z33 trans but he said he's super sure it's spot on. Also that's why I was saying that he's positive it's something vibrating against the body noise or noise that's internal from then drivetrain


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This is weird. OP i hope you can figure this out. Im dying to see what the issue is!

+1 im looking at this trans swap...don't want similar issue lol

Take out the center console and feel the shifter tunnel. It sounds like you've got the engine and trans hard up against the body somewhere, or at least it can move and hit it during idle.

I'm not looking forward to installing my Z33 box - I hear it's a super tight fit and still has to angle downwards some.

did you make your own rear crossmember or use someone elses?

Hey All,

I've had this up and running for a couple of years now. You are 100% rubbing on the chassis. It literally hits somewhere on every side of the trans/tunnel.

Also what deff said, when i was first fitting everything up i was hard up against the top of the tunnel.

What cross member are you using?

Lou

Man all these suggestions but none coming from someone who actually uses the trans......I bought a brand new OS giken twin plate, brand new cd009 when everything was swapped in. using maverick's adapter plate where the bellhousing was trimmed to fit.

The noise is super obvious on decel and it sounds like a fighter jet....before the old mounts (they were either stock or nismo) it would sound like a freight train coming off it's rails....now after my mech switched it to solid mounts....the noise is bearable at the most but still apparent.

I notice the noise goes away a lot when you muzzle the shifter....I want to say that's the best we can do at this point is just get a shit load of sound deadening in the area.

My buddy has the same set-up and gets the same sounds......the car feels and shifts great, grabs so hard that v8 stang, STI's are child's play. even my friend's s14 with 300+ versus my stock turbo set-up could only pull away from me by inches.

It sounds awful but it's definitely not mechanical, sounds like what loucal says about chassis rubs.

TS2BD clutch? What flywheel bolts did you use? Did you have to cut them shorter like the instructions say?




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So I've thought about this issue a lot lately lol as I had my GT3076R grenade itself (waiting on parts).

Here's what I have:

• Makes the noise slightly in neutral (clutch pedal out) and in gear (clutch pedal in) with the car stationary.
• Makes the noise BADLY under load (driving or rear wheels in the air with ebrake dragging)

My thoughts on causes are now only the following:

• Transmission is shifting hitting the body under load.
  (I really doubt it's this, as the shifter barely moves and I have clearanced the shit out of the tunnel, ensuring there's at minimum half an inch. I've also tested this by moving the transmission down another inch on its mounts, still makes the noise.)
• Resonance in the z33 transmission.

I think it's resonance. I'm using the S-chassis mount on the transmission with a crossmember I fabricated. If you look at the oem nissan mount it's a completely different design. It's also secured to the crossmember by a bolt nissan itself calls a "damper bolt". Nissan also uses a dual mass flywheel to smooth vibrations as well. I'm thinking this transmission is just super noisy by design.

Solution? I don't really have one, but I'm gonna build a new crossmember that uses nissan's mount system over the winter, but until the snow flies I'm just gonna drive it.

Could you explain to me how you did this please? It might help my cousin dealing with a similar vibration on a different car.

If clutch pedal is pressed in with the car stationary, doesn't that mean nothing is moving in the trans?

When converting from a dual mass to regular flywheel, people often talk about having more vibration and noise. I have seen threads on bmw and volkswagon forums about this.

You all realize that these transmissions right out of the box are extremely loud right?

Go on a 350z forum and you will see plenty of complaints about how loud they are and that is in a car that has much better sound deadening than our cars. I have about 3,500 miles on my setup and am making 400whp and the trans is perfectly fine, and loud as hell.

I wouldn't worry and go ahead and enjoy the car.

Lou

This isn't just this car being loud, trust me. This is some sort of resonance that vibrates the entire chassis, feels like the car is gonna come apart. Also the fact it happens at one part of the rev range is concerning. Resonances like that can be highly destructive.

Get a vibration measuring app for your phone. I used "Vibrations" on a samsung s6 edge. It uses the accelerometer and microphone to figure out the mechanical and audio vibration. It's pretty accurate surprisingly. I just set my phone on the valve cover and opened the throttle to 4000rpm. Then you can convert the vibration from Hz to rpm by doing this:

http://www.kylesconverter.com/freque...ons-per-minute

If you get a Hz reading of say 134, you know the vibration is occuring at 8000RPM or twice every crank rotation if your are revving the motor to 4000RPM and holding it there. Generally, if it happens in the first order, look at your rotating assembly (flywheel, crank, pistons/rods and balancer). If it happens at the half order (or less) look at your valvetrain. If it happens at the second order good luck, it can be a ton of things. Read up on vibration analysis in machinery for more on this. Hope that helps!

If the clutch pedal is pushed in with the car in gear it means nothing is moving in the trans. If the pedal is pushed in but the transmission is in neutral drag on the clutch disk and input shaft snub will still rotate the transmission a bit, but not a lot.

Has anybody used the mazworx sr to vq bellhousing? Also thinking of going this route, would like to know what the noise level is in that thing before pulling the trigger on a $900 part.

I'll be using it myself, haven't installed it yet. These transmissions ARE "noisy", but shouldn't be anything crazy. But they are louder than the stock trans for sure.


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yeah that defiantly gives me something to try. thanks.

are you 100% you ruled out the motor by putting on the sr bell housing? it sound like your tests of clutch in/out dont point towards the trans. Just trying to make sure you dont overlook anything.

just wondering: how high does your mount system hold the trans? I heard they hang below the frame rail with kits on the market

I can't be 100% sure it's not in the motor. It doesn't do it particularly badly unless the car is under load. Only way to be 100% sure would be to swap back to a known good sr20det trans. However I'm pretty sure it's in the trans as the car did not have this noise at all before the swap.

The motor mounts I'm using are filled oem ones. They feel similar to a buddy of mine's nismo ones, but they sit lower to help with transmission clearance at the top of the tunnel. It definitely hangs below the frame rails, but less so than some other z33 swaps I've seen.

I have the same issue here. SR20DET with Z33 transmission swap. The transmission is loud by itself, which is fine, but I also have crazy vibrations.

Hours were spent checking clearance to the transmission tunnel, and I think this is not causing this.

The transmission worked fine at some point in the past, but problems started when when a downpipe to engine block bracket was added to support the exhaust manifold and take weight off it (as I was having a problem with cracks). At the same time I changed the Z33 OEM rubber transmission mount to a polyurethane unit, which increased the vibrations to a level where you felt uncomfortable driving the car. Changed it back to Z33 OEM rubber mount, which helped. Then changed again to a hardened rubber mount, which is acceptable, but not good.

A rubber connecting mount (don't know the exact english word for this) was added to the block to downpipe connection, which only helped a bit. If downpipe and engine block are not connected, the vibrations are nearly gone. But then I have the manifold cracking issues again, and I don't know which is worse... ;)

Yes, this was checked again and again. This was an issue (which sounded different by the way), but the box was taken out twice and space was made (using the good old hammering method :))

This only occours at a certain point in the rev range (~4.5/5k rpm). Both when driving and also when reving stationary.

Just my .02 but I think its normal if your running a puck clutch. I have a similar issue with my ka-t setup. I had spec before and had crazy vibration around 3.5-4k on decel, did literally everything from mounts, bushings, driveshaft and even cracked open the bell housing and everything checked out.

Just rebuilt the motor and had the whole rotating assembly balance with comp bunny clutch for more power and right after starting up the car and driving down the block the noise was still there but less aggressive.

Its just "racecar" problems and something you have to deal with, running a puck clutch in any sorta car will make crazy noise having less dampening and stuff outside of oem shifter, mounts, flywheel etc will just make it louder than it should be.

Does it sound like this? Asked the guy and he told me the exact thing just being the puck clutch and is "normal" @17:33

ok so
the z33 transmission is always noisey, and being a SMF it will be even noisier then stock.
i wouldnt worry about it
we have done loads of conversions of the z33 box to RB, JZ and SR20's and most are noisey, unless its a totally new transmission then the noise is minimized
thanks

Nope, it doesn't sound like in the video at 17:33. In my case, we are also still running a dampened organic clutch...

It's not about noise. Don't really care about noise. It's about vibrations, as these can be harmful to other components.

I guess I will make a video next year...

Teambadrun what is smf?

So much fun

Single Mass Flywheel.

Thank you.

Are you running the harmonic weights that are attached to the back of transmission stock? I am not running them but do not have a problem with ls1>cd009. 4 cyl just put off a lot of vibrations naturally, the reason a lot come with balance shafts.

^What balancer shafts are you talking about? Pictures would be great.

He's talking about balance shafts that are OEM parts to engines like the 4G63

I know about the ag63 but he said harmonic weights attached to the back of the transmission. I've. Ever herd of that before.

There are 2, one on each side right below the shifter
http://www.slidegood.com/nissan/03-n...sion-weight-mt

if your going to pull the thing to pieces then maybe have a look at your spigot bearing in the back of the crankshaft as if the adapter plate sits the box out of line ever so slightly it can wear the spigot causing the input shaft to wiggle around.

Thank you. Man that's weird. I bought a new cd009 and it didn't come with those.

I sell new CD009's and I've never seen those lol

Makes sense because its an add on to the trans. I am not sure if they would fit with a custom trans mount in a s chassis( I took mine off before installing into car) but if I can find mine I could send them to whom ever if they pay shipping

Here is another pic showing where it sits. Its right at the tall section on the side before the shifter extension


http://www.soarerworld.com/forum/att...8&d=1358163820

Thanks for the input! Never heard of or seen these either :)

Thanks, will be replacing this.

I totally took off that dynamic dampener (as nissan calls it) and built my own cross member. I'm going to track down an OEM crossmember, mount, damper bolt and dynamic dampener and see if this calms down the vibration.

On top of this, I'm doing a Mazworx bellhousing as well as an ATI super damper. This motor better be smooth as all hell after all of this... If it isn't, something internal is broken or way out of balance.

So I've been tackling this issue in a more scientific manner lately lol. One thing at a time so I can rule out causes. Hopefully it helps someone else on here. I get a surprising number of PM's about this.

Anyways, I built a mount using the OEM 350z transmission mount. It made the vibration WORSE. So far using the 240sx transmission mount seems to be better. I didn't check if the 350z mount is harder or softer than the 240sx mount. I'll test that out tonight.

After this the next thing to try is the damper on the side of the transmission.

Weird! Keep updating this. Makes me nervous about mine.

make sure the engine exhaust system does not contact the chassis in any point. If you use a hanger for the exhaust to drivetrain, tie it to the trans crossmember like a factory mount (use the same sort of bushing the OEM uses).


I think you are having two issues. One is the mounting/vibration/noise related to the way the trans and exhaust system is mounted.

The other, resonance/vibration at specific RPM under load sounds like a pinion angle issue. The trans tail shaft and differential input flange need to be at identical angles (equal and opposite), with the trans higher than the differential so the driveshaft has a downward slope.

With the pbm max downpipe and s13 trans mount you can retain the factory hanger between the downpipe and trans mount with cd009.


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So I have run the car without exhaust, ensuring nothing is touching in any way. Vibration is still present.

Also the vibration is present with the car in gear and clutch in. The pinion angle was measured and set correctly. Its also not speed sensitive. I'm positive it's not driveshaft related.

There is another thread about this on here where the op mentioned it may be caused by worn input shaft bearings allowing some slop. Thats gonna get replaced when/if I do a mazworx vq->Sr bell housing. Next up is the damper on the side of the tranny and then the ATI super damper. Transmission rebuild and new bellhousing is the last resort.

I'm not of any help to your current issue, but when it comes time to buy that adapter shoot me an email and I'll cut you a deal on it!

Update: Did an ATI super damper, hoping to smooth things out a bit more. Motor is smooth as butter at idle now, still horrific under load.

There's a thread on here where someone else had a similar issue, and came to the conclusion the input shaft bearings on these trans are shit. I think that can be agreed on now.

Solution (I think) is to replace the input shaft bearing and do the mazworx bellhousing. If this doesn't fix it I guess time for a hollinger :naughty:

Well, if that the case, they're currently 10% off!

Any updates? Did mounting harmonic bits on the trans help?

Not much of an update yet. I drove it the rest of the summer with the vibration present. It survived a bunch of track events and some street abuse just fine. So I'd say the vibrations this trans puts out are not detrimental to longevity.

However I haven't tried the OEM nissan vibration dampers. ATI super damper and different mounts all did absolutely nothing. If you have this vibration I'd say it's likely internal.

I have purchased the Mazworx bellhousing kit as well as new input shaft bearings. I will be doing this over the winter, then will report back here in the spring!

Hate getting those underlying issues, you've done a swell job of sorting out the bs and doing some research +1 for that. Hope this is the final fix

Update: I installed the new bearings and mazworx bellhousing. Vibration still present.

However the vibration doesn't seem to be a "problem". I said fuck it, drove it all summer, hit a few drift events, and the transmission hasn't had any issues. Shifts nicely. Just sounds like the car is coming apart at 4000RPM plus.

I'll be buying a new OEM Z33 trans over the winter and installing that. If that doesn't fix it I guess I'll just live with it.

I cant be bothered to go back and read the whole thread, but could it be the propshaft out of balance?

jack the car up so its arse is right in the air and take the prop off and 'drive' it.

I had this same issue after installing my mazworx bellhousing with the driveshaft they provided. Ended up being the universal joint not being lubricated properly.

When I was holding the driveshaft (off the car), i grabbed the u-joint and would move it around and noticed a few dead spots where it wasn't smooth and sort of catching a bit. I had Drivelines NW replace the U-Joint and voila, vibration gone.

So to close up this thread. Ended up buying a brand new from Nissan cd00a trans. Vibration and noise is still present. These transmissions are just insanely noisey. The chassis vibration is just a factor of my motor and trans configuration. I'm going to live with it till something lets go.

Solved! (Mostly)
 

So I'm bringing this back from the dead. I never got over this vibration. With the latest Covid lockdown up here I've had some time on my hands so I went full science on this. This is gonna be a long one.

I went and setup a Raspberry Pi and hooked up two accelerometers to it via an ADCDAC expansion board. Parts I used were:
RaspberryPi: https://www.raspberrypi.org/products...-pi-4-model-b/
ADCDAC board: https://www.abelectronics.co.uk/p/74...xpansion-board
Accelerometers: https://www.digikey.ca/short/4c5fwj

I then wrote some code to record the vibrations from each sensor:
https://github.com/linds14sr20det/race_car_avc

For the setup to measure this vibration I attached one accelerometer to the transmission (unused bolt hole near the shifter bracket) and the other sensor to the transmission crossmember. My trans crossmember setup uses the 370z mount as it's fluid filled and _should_ dampen vibrations better than any of the other mount solutions, or at least that's what I thought.

https://imagizer.imageshack.com/v2/8...924/0qSmVx.png

Here's the first graph of engine vibration (blue) vs. chassis vibration (red). This is a recording of me revving the engine slowly from idle to 4500rpm. As you can see engine vibration increases as the rev's rise with not a lot of chassis vibration until you hit 4000rpm when chassis vibrations exponentially increase and are now stronger than the engine's vibration. This is a clear resonance in the chassis. The force the chassis is experiencing here is about 4g's. Considering the trans mount supports over 100 lbs, this is actually a pretty significant force. I wouldn't be surprised if over time this cracked the crossmember or the chassis spot welds.

If you zoom in on the graph you can also see that the vibration occurs at ~150Hz. This works out to the equivalent of 9000rpm (150 cycles/second * 60 seconds/minute), which actually makes sense. 4 cylinder engines are inherently unbalanced with a pronounced second order vibration (vibration at twice engine speed). So this supports a resonance at 4500rpm. Also explains why these trans don't have this problem behind a VQ35 or an inline 6.

Okay so the next step was to confirm the crossmember is the vibration transfer path. This is easy to do, support the trans on a floor jack, remove the transmission mount, and bolt everything back up. Since the transmission is no longer connected to the crossmember, we would expect to see little chassis vibration if the trans mount is the culprit. If it isn't the source of the vibration we should see no change.

https://imagizer.imageshack.com/v2/8...923/q9yjKp.png

Pretty dramatic decrease. So we know it's the trans mount causing the problem.

There are 3 ways to reduce vibration transfer from all the reading I've now done.
1. Stiffen the receiver (ie. thicker floorpans and a roll cage. This is a street car so nope. Also explains why s-chassis with cages aren't as bad for this vibration)
2. Reduce vibration at the source (Increase the mass of the transmission, add a dual mass flywheel, change the gear mesh patterns, swap to an inline 6, etc. Not gonna do those either.)
3. Soften the engine mount. Vibration elimination has two parts, isolation and damping. Damping increases vibration transmission to the receiver but reduces the peak amplitude. We want to isolate the vibration and to do this we need to soften the engine mount.

To test this theory, I went and grabbed two valve springs from a vq35de. Since a 4 cylinder second order vibration is only in the vertical direction a spring is a perfect candidate for the mount isolation. This is also how jaguar used to mount it's transmission back in the 70's and 80's so this isn't as hair brained as it seems. Anyways, the VQ35 springs were soft enough they support the weight of the cd009 but compress about an inch each. So I'd ballpark them at a spring rate of 75 lbs/inch. Here's the graph:

https://imagizer.imageshack.com/v2/8...923/JIJOpM.png

We have a winner. Chassis vibration is way reduced and you actually can't feel the buzz or hear the floor resonating anymore. So I'm going to build out a more permanent version of the spring trans mount and report back on it.

Wow. What an incredible journey

Your diag process and documentation should be applauded

You seriously scienced the shit out of this. Huge kudos to you, good sir.

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Thread stickied. Excellent work OP.

Dude this is legit AF..... I knew CD009s were noisey but this is insane. But this leads to think its something internal to the tranny?

Is the vibration the same if you remove the driveshaft? I've read about driveshaft pinion angles and stuff?

What are your thoughts?

Maybe change fluids I know this helped for me moving from shockproof to amsoil. But not sure how significant is your vibrations.

With a sprung transmission mount isn't the driveshaft angle going to be variable while driving the car and over bumps etc? That seems like it might introduce some weird vibrations.

Kudos to you for actually finding the source though. Interesting that the characteristics of the I4 engine introduce this vibration to the transmission that doesn't happen with the V6.

This is absolutely fantastic. Well done OP!!

So I tested this with the driveshaft disconnected, no change at all. It is entirely related to the mass of the transmission and the way the trans case carries the vibration to the chassis. Weight of oil will help gear chatter related to switching to a single mass flywheel, but won't change the fact this trans does this in neutral as well. Resonance is a function of the natural frequency and mass of the object, in this case there isn't much you can do to the trans to change it.

You're totally right, springs alone would do some wacky things for driveline angle. When I finish designing my trans mount I'll be posting it here. I think the key is to have the springs "hover" the transmission just above and below bump stops. So any large bump has the trans hit a rubber bump stop that limits the change in angle. That being said if you were to watch how much a stock mount moves it's easily half an inch if not a full inch.

Thank you so much for your commitment.


You are a hero

I may be interested in buying one of these mounts from you.

Same if I have issues with my setup as well. I'm using the gk mount so we'll see

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