Solved: CD009 trans on SR20DET - Vibration at 4000rpm? (Posts #79, 108)

[canadians14sr20det]

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

[hanzbrady]

Originally Posted by canadians14sr20det

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

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

[konjiki7]

Originally Posted by canadians14sr20det

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

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

[TheRealSy90]

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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[Sailor]

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

I have purchased the Mazworx bellhousing kit as well as new input shaft bearings.

[canadians14sr20det]

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.

[gaz_moose]

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.

[Kintaro_Oe]

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.

[canadians14sr20det]

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.

[canadians14sr20det]

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.



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.



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:



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.

[lok]

Wow. What an incredible journey

Your diag process and documentation should be applauded

[mr.nismo.]

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

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[mrmephistopheles]

Thread stickied. Excellent work OP.

[slider2828]

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.

[canadians14sr20det]

Originally Posted by slider2828

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.

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.

[slider2828]

Originally Posted by canadians14sr20det

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.

Thanks for your clarity.

I thought you were revving the car to 4500 and beyond... Just thinking oil should help it a bit and I do like the idea of trying different mounts, maybe with lower durometer like driftfreaq mounts.

[TheRealSy90]

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.

[canadians14sr20det]

Originally Posted by TheRealSy90

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.

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.

[TheRealSy90]

Originally Posted by canadians14sr20det

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.

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

[mr.nismo.]

Originally Posted by TheRealSy90

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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[Antihero983]

This is absolutely fantastic. Well done OP!!

[97kouki1J]

Thank you so much for your commitment.


You are a hero

[jr_ss]

Have you given thought to trying other mounts? Such as but limited to Nismo, energy suspension, etc? It would be interesting to see this comparison.

[spooled240]

This is very interesting as I have been trying to figure out a resonance vibration on my KA for years. Contrary to your experiences, the vibration in my car is felt anytime the engine is revving around 2200 rpms (free-rev clutch in/out or driving in any gear) which means the source is the engine itself. Replacing the harder Nismo engine mounts with softer, liquid-filled motor mounts perhaps off an older BMW 5 series is what I'm going to try.

Positive rep for the very methodical and technical approach to testing and updating this thread with findings!

[canadians14sr20det]

Originally Posted by TheRealSy90

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

Originally Posted by mr.nismo.

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

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I won't be building and selling these as I don't want the headache that goes with all that. I will however provide the plans for whatever I build so anyone else can replicate it, or at least have a fabricator build it for them.

Originally Posted by jr_ss

Have you given thought to trying other mounts? Such as but limited to Nismo, energy suspension, etc? It would be interesting to see this comparison.

I have already done this. I've tried:
- OEM s14 mount
- OEM s14 nismo mount
- OEM 350z mount
- OEM 370z mount
- Generic energy suspension bushing

The 350z mount with the damper bolt was the best, but only marginally better than an OEM s14 mount. Frankly none work well as they are all not designed to work in this application.

Originally Posted by spooled240

This is very interesting as I have been trying to figure out a resonance vibration on my KA for years. Contrary to your experiences, the vibration in my car is felt anytime the engine is revving around 2200 rpms (free-rev clutch in/out or driving in any gear) which means the source is the engine itself. Replacing the harder Nismo engine mounts with softer, liquid-filled motor mounts perhaps off an older BMW 5 series is what I'm going to try.

Positive rep for the very methodical and technical approach to testing and updating this thread with findings!

This is probably normal. The second order vibration moves lower in the rev range as the 4 cylinder gets bigger. As the KA is a bigger engine this would make some sense. You can use an app like Vibrations! on your phone to determine the frequency of the vibration. If you have a vibration of ~70Hz at that RPM it's a second order vibration and your plan for the 5 series mounts would probably help.

[jr_ss]

Originally Posted by canadians14sr20det

I have already done this. I've tried:
- OEM s14 mount
- OEM s14 nismo mount
- OEM 350z mount
- OEM 370z mount
- Generic energy suspension bushing

The 350z mount with the damper bolt was the best, but only marginally better than an OEM s14 mount. Frankly none work well as they are all not designed to work in this application.

I figured this would be the results. It only makes sense, since they are sold as a higher durometer rubber. Thanks for confirming!

[foreverdeath]

Did you ever make those plans? I get the same vibration with a cd009 and turbo K24A2. After 4k rpm the chassis is vibrating pretty intensely, but flat out I cant notice it feel it.

[canadians14sr20det]

Originally Posted by foreverdeath

Did you ever make those plans? I get the same vibration with a cd009 and turbo K24A2. After 4k rpm the chassis is vibrating pretty intensely, but flat out I cant notice it feel it.

Yeah that makes sense. Under full throttle the time you spend at that rpm is limited so the chassis has trouble getting into resonance, as well as the gear lash stays tighter inside the trans.

I did make the mount but it also wasn't a huge help (though it worked great free revving the engine). Under cruising load the vibrations are being transferred from the trans through the driveshaft to the rear end. I have solid subframe mounts so that probably isn't helping. Guessing most of the people on here have solid subframe mounts as well. Anyways, here's my design:



The rubber mounts on the side mount to aluminum L-brackets that bolt to the stock location. Like I said, works great with no load on the engine, just free-revving. Inspired by this jaguar mount design:



Since this still doesn't work under load I'm gonna try switching my subframe mounts from solid aluminum back to nismo rubber bushes. If that doesn't work I may try a carbon fiber driveshaft. I'd like to throw a dual mass flywheel on or a guibo on the driveshaft but both of those options would require crazy custom machining. Honestly I may say fuck it and go back to a 5 speed.

Originally Posted by mechanicalmoron

Trying it without the damper does not eliminate the damper - it simulates a really-bad-case (I only don't say worst because half a damper could be even worse... but worst possible, right?) damper damage scenario - it's highly inadvisable to rev it like that without a damper, even briefly.

I have no idea what you are talking about. There is no damper that is integral to the CD009.

[mechanicalmoron]

Trying it without the damper does not eliminate the damper - it simulates a really-bad-case (I only don't say worst because half a damper could be even worse... but worst possible, right?) damper damage scenario - it's highly inadvisable to rev it like that without a damper, even briefly.

[spooled240]

I think swapping the solid subframe bushings out is a good plan. I have solid aluminum bushings on my subframe and I get noticeable vibrations from the rear of the car right around 2200rpms in lower gears. 2200 rpms is also where I get resonance on my KA 5 speed. I just ordered Nismo subframe bushings because it is bothering me so much.