Harsh vibration at 3000-4000rpms, trying to narrow it down (not stock)
 

So over the last month or so, my BRZ has decided to have something go wonkey and I can't figure it out...

At around 3000rpms the car has a noticeable vibration coming from the engine/transmission. It lasts up to 4000rpms and mellows down to tolerable. Sometimes its less noticable than others, but sometimes its pretty severe. You can feel it through the pedals, shifter, steering wheel, seat, etc. but it doesn't feel like the car is loosing any power or having other issues just the vibration.

I do have quite a few mods, and my headers (Revworks) actually developed a crack in the last couple weeks I had to have repaired. Its possible that crack was a result of said vibration but I'm not too sure.

List of drivetrain/engine related mods:

TRD Intake
Revworks Header
OFT Tune for UEL on 91 (just updated the tune, didn't change anything)
Nameless Catted combo pipe w/out resonator
Legsport Muffler (stock midpipe)
Kartboy exhaust hangers (only for the muffler)
STI engine mounts
AVO Transmission mount (slightly modified to reduce NVH)
Kartboy rear shifter mount (installed about 3 weeks ago in an attempt to alleviate the concern, no luck)


Almost all of these mods I've had for a year now with no issues, its only in the last month or so I've had noise/vibration issues.


I've also noticed a rattling noise at time coming from what sounds like the front of the transmission or shifter assembly. In 3rd gear at about 4500 rpms I heard what sounded like a bolt rattling but it wouldn't replicate in other gears at similar RPMs and was hard to reproduce. The car has other noises too, like a rattle when at a stop when I put the car into neutral when braking for said stop. It sits and rattles a little at idle.

Ideas for what could possibly be causing it:

A loose bolt somewhere I can't find (I've checked everything pretty thoroughly)...

Failed mounts (transmission mount maybe failed with the AVO insert? The engine mounts seem good)...

Something bent/broke when jacking up the engine/drivetrain to install the overpipe/front pipe...

Clutch/flywheel/throwoutbearing/shifter fork failure of some kind...

Internal engine failure of some kind...

No other ideas...

So I'm just looking for input. I might just throw the stock header/cat section back on to test and see if that fixes it but I'll have to wait a week to do so, and maybe back to the dealer after that to see what they say (I used to work at said dealer, so I'm not worried about the mods with the dealership).

Anyone else have any other thoughts or similar problems?

Does it happen when standing still, or just when moving?

All gears, or one specifically?

And all the time on said rpm-s, or only when engine/exhaust is heated up? (recall one case when rubbing/hitting started only on hot exhaust, that might be harder to catch when checking everything cold)

Standing still its less noticeable but still there a little bit. Sometimes not so much at a standstill, so I would say more so when driving.
Heat doesn't seem to be a factor, it can happen when the engine/exhaust isn't warm or after driving for half an hour.

Man, nothing jumps out. Maybe look for exhaust interference somewhere?

Small update: Other than some small oil seepage at the top of the engine, I did just discover my clutch pedal is ultra-squeaky now (throwout bearing) starting to wonder if its the clutch assembly...

I had some exhaust interference at first with the nameless, but I fixed it with a dent and some heat wrap.

Time to drop the trans.

Ill have to take it in for that. Can't do that by myself.

WHere is your oil seeping from on top?

Does the clutch engagement feel crunchy as well? If not, maybe try lubricating the top of the clutch fork first and see if that solves the squeaky sound.

Oil seems to be from the top of the timing cover seal or possibly the middle of the top of the block.

The lubrication might help temporarily, I used that trick on my old Impreza, but it won't solve the vibration.

I found the nameless pipe was a bit too close to the chassis and I adjusted it, and I also swapped the AVO trans bushing for a Kartboy one I had sitting around...

No change.

I just went under the car while it was running and heard clacking from the pasanger side cylinder head :/

I'm starting to think I might have over-revved a few weeks back on a downshift and bent a rod or something and didn't notice it at the time...

My best guess would be a loose or broken motor mount.

You might wish to check them ...... again.


humfrz

I swapped out to the stock exhaust, even lifted the engine a little to check the mounts... No change. (FYI I have the STI engine mounts)

I'm going to take it in to the dealer, no choice at this point.