Qingdao

iTrader: (3)

I am having a vibration in my 4 port FC engine coupled to my S3 factory transmission. Its shaking like a soab at 4k and above under load. I have yet to just free rev the **** out of it, but I will try that soon to rule out any pure engine possibility's.

I have recently replaced the drive shaft (that didn't make the shaking go away). I also recently replaced the transmission mount (that didn't solve the issue either).

I am running a really strange Exedy 3 puck clutch.... Maybe this is what happens to them when they wear out????? But I only have like 7 or so thousand miles on it. Could it have worn out so quick?

I've had this engine/transmission combo for about 20k miles and never experienced vibrations so I don't think its flywheel/cw related.


Any ideas? I'm beating my head against a wall trying to figure this one out.

GSLSEforme

Any gear,any speed? Stop immediately if let off gas? Push in clutch,put in neutral,shut engine off ? How does clutch feel,launch car hard much,engine mounts ok?

Qingdao

iTrader: (3)

Hmmm can't recall if it lets off when I let off the gas. I want to say yeah.

No vibrations in neutral or clutch in. The front u joint was bad (the car is easier to get into gear now), but it was not the source of my vibration.

I am thinking motor mounts. I put a pry bar on them today and the left front one is kinda soft. That motor mount should experience stretch when the engine is pumping right? The right side mount is solid.

I am pretty rough on the car. No squealing tires but I do put it though its paces. I know I need to get a Tii transmission and 9" rear, but that would just lead to a bigger turbo and studded engine, slippery slope.

GSLSEforme

Vibration felt in front,in shifter,in back of car(in seat)? Can you duplicate this without vehicle moving by revving engine? Replacement driveshaft new,known good,serviceable u-joints,balanced?
Has the left motor mount had any oil leaking on it possibly weakening rubber? It's possible if engine making enough power,mount could be stretching allowing engine to lift/rotate and change driveline angle under hard acceleration.

If you feel vibration in shifter/back of car under acceleration,but steady cruise not so much, consider checking driveline angles...trans/driveshaft/pinion. Use angle finder/protractor to see what your angles are. I use a magnetic angle finder,cheap,got this one at ACE hardware. You can get them at Homies,lowes. I'd been chasing a vibration at speed in my SE,replacing u-joints in driveshaft helped problem but fix was short lived. Broke 2 replacement u-joints in rear 3 months,1 from an aggressive launch,2nd at speed which was scary(pucker factor),shutting engine down,pushing in clutch to stop shaft from spinning,so glad i made decision to keep heat shields in place when installing streetport exhaust,was only thing from keeping driveshaft from hitting ground. Heat shields have some interesting witness marks...shopped around for a replacement driveshaft,settled on one from Mazdatrix,had it checked for balance before install. Vibration much lessened but still there(Did i mention i hate vibrations).
Two winters ago,went thru complete suspension:springs(RB)struts/shocks/bushings/upper lower links in back/anti roll bars/wheels & Tires. Last year to level out stance of car,i cut 3/4 of a coil off rear springs 1/4 of coil at a time and checking ride height AND roadtesting. Would like to cut total of full coil but the 3/4 of coils cut woke up the vibration with a vengeance.

Upon checking driveline angles i had what i felt was too much negative pinion angle on differential and needed some way to bring it more positive. I'd seen the T3 adjustable links on their website,but didn't want heim ends on links on my car. Took a spare set of lower links that came with a GSL diff assly i have and cut one end off each removed about 2" of link length and welded 4 link adjusters i cut out of an old Mustang setup i had in place then welded bushing housing back on. Using the stock links for length,i adjusted my replacements to be about1/4"shorter and installed them and drove car,better. Adjusted slightly more,better still. I was able to use my friend's drive on alignment rack to measure before/after pinion angles. So far have changed pinion angle just under 1 degree +.

Best place to get reading on trans angle is drainplug,perfectly perpendicular to trans housing. Driveshaft is easy,easier with no heat shields. Pinion angle can be checked by removing driveshaft and placing angle finder right on companion flange(clean all rust/dirt to get a good reading) Cars weight needs to be on suspension to get accurate readings. Car can be put on stands level but rear needs to be supported by axle housing to load rear suspension at ride height.

It's a pain removing back of lower link to turn end to adjust and recheck. I want to remove link completely and cut off and weld in opposite thread adjuster(like i should have from beginning) so locknuts can be loosened and links shortened in place,remove driveshaft from pinion and put angle finder on and dial in pinion angle i want. Dealing with some stuff currently and along with some other things,have had to put this off for awhile. Hoping posting what i've done to alleviate vibration will help your situation.

Qingdao

iTrader: (3)

DEFINETLY in the shifter. Not too much from the rear at all.

You know I was JUST thinking about pinion angle recently, but I've never had an issue with it as far as I know. I've been running this height for about 2 so years. I guess this is as good an excuse as any to put the car on the alignment rack at work and check the angles. (I have a feeling they are super bad)

The shaft I put in there was good. No binds or malformaties, but I'd never used it on anything else. When I put it in I didn't notice a change in the vibration; just easier to shift.

Yeah I had a squeeze out of my front cover high pressure oil circuit a few years ago... and that area is kinda nasty. Its oil soaked. I planed on replacing it tomorrow when i get to work, and I'll try to free rev it on the highway on the way to work see if its engine only vibration.

Qingdao

iTrader: (3)

I'm betting on W/P failure.... I came to that because I just notice today that my coolant is low and coming from the water pump's weep hole. And I've read that a bad water pump bearing will cause the shakes.

GSLSEforme

If you can duplicate that condition with car sitting still,would be real easy to slip belt off and rev to see if vibes gone.

Qingdao

iTrader: (3)

Yup it was the water pump causing my vibration.

Toruki

Nice find.