All solid mounts but engine = shake at RPM?
 

I have solid (delrin) bushings everywhere except the motor mounts. (I have them, but un-installed)

The car had no shakes and drove fine, then I did a turbo drive train swap with a ACT lightweight flywheel. I purchased a s4 counterweight from my friend as my car is a s4 motor.

I realize the counterweight may be wrong, but I have also heard that having solid mounts everywhere but the engine mounting bolts can also lead to vibration. The vibration can be felt everywhere: shifter, seats, dash, radio area, the works.

My question, specifically, could my car be shaking due to solid mounts everywhere but the motor?

Other notables: Driveshaft felt fine, Counterweight was locktite'd and tourqued to ACT specs, Flywheel was impacted on. Delrin EVERYWHERE except mazda comp frond diff mount and oem motor mounts.

Thanks.

And yes I searched.

I forgot to add, my shaking characteristics are:

Normally Smooth from 0-3500 RPM, then raising shake with RPM.

Under WOT I did notice one time where it smoothed out at high RPM, maybe 6500-7000. I do not know if its every time as I don't want to damage the engine in any way so I only WOT'd to redline when we first noticed it.

sounds like that used counter weight is biting you in the ars....

If you had the vibration all over the RPM range I would say it was the mounts... I have a 240 with soild everything and it shakes like hell.... howeverthe fact that your seeing it at 65-7 ... Thats no good...

Yeah, I am afraid that if I put in my solid mounts it will get worse if it is a wrong counterweight. Right now it is drive-able and I am going to replace the engine/weights with a balanced unit in 3 months so it doesn't bother me to keep it low RPM for now.

Nobody has said driveshaft u-joints yet. Get that checked out, since I'm sure you installed a used driveshaft they could definitely be worn out.

It felt fine when it was out of the car. My friends 300zx just had a bad u-joint so I was sure to check it before I put this one in.

Vibration is from 3.5k and up, with unconfirmed smooth out from 6.5-7k.

You need a counterweight from an rx-7 with an automatic transmission if you're running with an after market flywheel

^ Did you even read the first post??

If you had the right counterweight good chances you will have no vibrations, for even better results get the right counterweight to start with, then get the rotating assembly balanced. There are plenty of people with solid engine mounts that experience no vibrations.

Thanks, my question though, is in the unique combo of all solid mounts EXCEPT engine, will the proper counterweight still cause vibration due to the transmission being tied to the car and the engine allowed to wiggle.

You need to use a counterweight to avoid vibration

Other then the fact that the counter weight is used I don't see that being a problem since you are still in the correct series. Even so I dont see how a used conterweight could cause this w/o obvious visual signs.

He has a counterweight!!!!!!!

you cant even install a lightweight flywheel without one!!!!!!!!!! its impossible!!

OK..let's get real here.Question answer: Your car wouldn't be Shaking because you replaced the Mounts..I Replaced the Tranny Mounts With Solid,and didn't bother to do the Engine mounts..It just Made the car more Vibrating through the chassis,as you would expect when the Transmission is SOLID to the Chassis.You feel alot of Gear Rumble,etc..But not SHAKING..the Shaking Could be the Driveshaft.YES the driveshaft!..IF the driveshaft wasn't replaced as it Was before.MY Suggestion would be to Jack the car up and Turn it 90 Degrees at the differential and See if the Vibration goes away...then try Another 90..then another 90..That would RULE out Driveshaft after this was done.

If the car is vibrating only when driving and not at idle, then its probably a driveshaft issue.

Also check to make sure that no part of your exhaust system is touching the underbody.

its when driving and at idle.

Then I'd say he put a S4 manual trans counterweight on. You can change the motor mounts, but they won't fix anything.

The car would vibrate, yes.

I put a S5 Counterweight on a S4 Motor.
My friend pwn'd me.

To answer this threads original question,

No, having all solid mounts except the engine mounts will not cause shaking at high RPM.