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.