Vibration Problem suggestions **HELP**
 

So my FC vibrate/shakes a little more then normal in 4th gear around 50 MPH. But as I drive faster the vibration/shake lessen. I've taken the FC into a LineUp shop and got the Sub-frame front crossmember adjusted,
changed front inner tie rod- which was bent,
replace wheel that was not rounded,
adjusted my uneven racing beat end-links ( yes RB makes adjustable end links),
Alignment front and back of the car,
replace drive line (it was bent)
STILL VIBRATES at 50 MPF***H....:scratch:


:blush:

A's and B's I'ver heard..

Could tire walls from the inside be a problem/if so replace tires?
U-joint bolt loose?
new rims ( all mine are good...)

SOOOO.. Suggestions GUYS!:confused:...

You try having the tires balanced?

Yeah all 4 has been balance last weekend.

I had serious problems with those damn clip on wheel weights falling off of my vert, causing a similar issue.

I had my wheels static balanced and sure as shit, problem solved. This is just FYI for anyone else who reads this.

To the OP, I would jack the car up and try and rock the wheels. I am thinking possible wheel bearing failure.

Static Balanced... Sake still there SMH...

I need a bit more information on this one, does the vibration only seem speed dependent? Or does the vibration happen with RPM change?

If it is speed dependent, you should be able to feel if it is coming through the steering wheel or if it feels like it is coming from your seat.

If it is RPM dependent then, you are looking at an engine/driveline issue.

try rotating the tires- does it change?

drive line has been replace...reduce the shaking a lot.. but the vibration I'm feeling is def. in the steering and a little of the entire car.. it's not a dangerously monster shake.. but more of a vibration that shouldn't be there.. It's driving me crazy...

you have new wheels? any spacers?

yeah I have got all the tires and wheels checked. they are good. as well.. ENGINE is perfectly fine.. Starts, RUN, REVs like a beast as it should.. just when I'm going 45-50 the car start to vibrate/shake a little.. the faster the speed that less shake.. but thats just all physics right there.. shake is still there-

No spacers.. Wheels will come in after coilovers. I might give up on the shake problem and take the car into a shop if i cant find out and fix myself.. which is a pain...

Speed dependent. For sure.

I'll chime in. Your car's vibration at 4th/50 is due to a resonance or natural frequency in the drivetrain or suspension. There ar two things that can cause it: a small unbalanced reciprocating mass, or something loose. As Capn pointed out, you can find out more by trying to get the resonance to show up in another gear at the same rpm = probably engine/drivetrain. If it only happens at 50 in 4th or 5th = probably wheel/tire related.

since you've already done quite a bit of work on the wheels and suspension I'd suggest looking at the drivetrain. In the years I've had my Rx-7 I've had to replace the sump engine mount, the transmission mount and the forward differential mount due to the rubber separating from the metal bracket. It's surprisingly common and if one or more of these parts have failed it could lower the natural frequency of the driveline into the operating range and cause that awful vibration.

One other thing worth looking at. Check the tire tread runout for each tire. I once had three new Michelin tires develop separations in the tread (air pockets between rubber and belt) due to a manufacturing defect. It caused an awful vibration at road speed that was difficult to diagnose. They replaced them under warranty but I had to wait for each one to fail first. Very frustrating.

These are just suggestions to try and help. Let us know how you resolve it.

do you still have PS?

I have not check the drivetrain yet. Ill run all these checks and let you guys know. Thanks for the informative knowledge and suggestion fellas!

if it is speed dependent, also check whether or not the vibration happens when the car is under load or just while cruising on a flat road. if it happens under load I would think there is a loose diff mount, or transmission mount.

And if it is just while cruising you want to check your bearings in your front wheels, and your tie rod ends up front.

Hell, it could be a loose body panel or something.

You said you replaced the "drivline" do you mean driveshaft? My buddy had a simlar problem with his GTU. We put in a new balanced driveshaft and it went away completetly.

Yes the driveshaft I believe was bent. And replacing it made a big improvement. But still that annoying vibration while cruising. I'll def. Check my mounts etc. This weekend.

Maybe I am stupid...but I have no idea what you are saying. :)

If the driveshaft was bent, it's vibration could have damaged the transmission mount or front diff mount.

My bad for the typo*** shake. Static balance. Just look it up =]

Gotcha now. :)

This sounds like my issue, 3 months and counting, finally narrowed it down. It started with a steering shimmy and now has ended in a body vibration issue. I replaced a slightly bent wheel and new wheel bearings

1. My alignment was bad, got it fixed, in spec now. Steering vibration/shimmy gone 90%

2. After getting my wheels and new winter tires rebalanced 5 times at the local DS Tire, I ended up going out of town to another DS Tire store, morons at the first locations don't know how to balance tires. GET a dynamic balance not static. Yes, the weights look ugly on the outside but we are after functionality, not looks. Steering vibration/shimmy gone 100%

3. When hitting 70mph, I would get a really bad body vibration. I could only describe it as something engine/drivetrain related out of balance. I took my car to a drivetrain shop last week and had them check my driveshaft. Sure enough, mazdatrix screwed me and hadn't mounted the rear u-joint corrently. The front of the driveshaft was SLIGHTLY not straight but still within spec, got it straightened.

Car back on the road, the vibration at 70MPH (5th gear) is still there. Having solid mounts, I know none of my bushings are bad. I noticed, if I rev my engine in neutral if I hit 3000rpm or higher, I get odd vibrations, with or without clutch pedal pushed in. I have always got "harmonic" vibrations at these rpms, but it just didn't seem right this time.

I went on the highway, 5th gear, 70MPH. Body vibration shows up. I noticed at 70mph its around 3500rpm. What I did was i held this rpm and pressed the clutch pedal to determine if it was engine or transmission related. Come to find out, as soon as the clutch pedal is pushed in, at the exact RPM i get the vibration, I could feel a "lesser" but still same pulsating vibration. Seems like my engine is on its last leg.

I have always had slight vibration issues with this engine and suspect the previous owner starved it of oil at one point. Now with 152,000 miles on it, I believe it has developed for the worse and bad oil control rings do not help. When I replaced my flywheel I noticed some play in the e-shaft, my guess is something internally wore out causing excessive play to the point I can't drive above 3k rpm. Having extra load (as in 5th gear) on the engine makes the problem show up extremely well. The vibration is there in neutral and gears 1-4, but 5th shows it well.

Now, for you:

1. Check balljoints. Can only be done with car on ground. Grab tire at the 12 clock position. Make sure wheels point straight. Now tug back and forth hard. Any clicking/clunking?
2. Check alignment
3. Check tie rods
4. Check steering rack (make sure bushings are good and bolts are tight
5. Have wheels dynamic balanced.
6. Check rear DTSS bushings, swing arm bushings.
7. Check struts/shocks
8. Is there play in the steering wheel? If so, you could have a bad rack or one that needs adjustment
9. After that has been covered start looking into engine/transmission vibrations. At this point everything suspension/steering related has been eliminated. Why was the driveshaft bent? Bad transmission shaft? Rev engine in neutral at the exact rpm you get the vibration at 50mph. Is the vibration slightly there?
10. Check your engine and transmission mounts!
11. Check that the fan (if stock) is seated properly on the engine. Check the nuts that hold it together. Sometimes if this is bad, it causes vibrations.

By what you describe, it sounds like a bad wheel balance but I can't say 100% without seeing your car. When did the problem begin? A bad u-joint is SPEED DEPENDENT and will get worse the faster you go. They should have been checked when you had the drive shaft fixed.

Anyway, hope this helps you out.

@ jjcobm::

Wow you your situation/problem is almost on the pin point of what I'm experiencing. Driveshaft was bent from some crazy drifting days.. And I will definitely run down the check list you provided. Thanks all! And will update as soon as I get the chance to get under my
Car and take a closer look.

Had a vibration in the 50mph range years ago. Drove me nuts checking all possible areas, trans back as that's where is vibration could be felt. Trans mounts were new but couldn't find the problem, then decided the only area left was the motor mounts. Right front split causing the drivetrain to be slightly off center. Replaced the mounts and no more problems. Sounds simple but it took months before the brain decided to look to the front.