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PostPosted: Wed Apr 25, 2018 8:41 am 
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Location: CT
RichZ said, "Would like to go to this event but, my Z has been in the shop most of the winter. I brought it in for an oil change and minor vibration. They replaced the rotors, brakes, tires and did a 4 wheel alignment. The car was then literally bouncing when I drove it. Would not drive in a straight line. Brought it back, They replaced a steering control arm and shocks. Now it was back to the way I started, still with minor vibration. I had 2 tires go flat within 3 weeks at $200 each. Six months to get a warranty refund. And now, the vibration is getting worse. When I been driving for 5 minutes, the rear starts to rumble and the whole car shakes. Two minutes later everything becomes quiet again. Research tells me it could be a CV joint".

Bent wheel rims? Unbalanced drive shaft? Differential needs readjusting? Worn or dry universal joint? My buddy had a built '56 Chevy with the same problems (except the growl in the differential); it was a single slightly bent fan blade. Once he reached highway speeds the fan de-clutched and the vibes went away until the fan engaged again. Drove him nuts for nearly a year.

The coming and going of your rumble and vibrations probably has more to do with the difference in the type of driving you're doing, than in the amount of time it has been driving. In other words, if it takes you 5 minutes to reach the highway and two minutes to reach your exit, your speed or uphill load conditions might have changed?

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Last edited by Frank T on Wed Apr 25, 2018 12:18 pm, edited 1 time in total.

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PostPosted: Wed Apr 25, 2018 11:41 am 
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Rich,

Sure sounds like major wheel and or tire imbalance to me. Curious as to what brand tire and if you changed tire sizes? Who did your brake and alignment work? Was their any recent history of hitting a big pothole or curb? Are you getting the vibration feeling at the steering wheel also? :?

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John Kish
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PostPosted: Wed Apr 25, 2018 12:04 pm 
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Yeah, John's right ~ I forgot to ask if the vibration was noticeable in the steering wheel or in the rearview mirror, or both?

Also, could they have mounted your new tires to rotate backwards? (little arrow shows rotation) or rotated your old tires incorrectly and swapped sides with them (such as L/R to R/F)? As you know, radial tires must only roll in one direction so they have to remain on the same side of the car. If you roll them "backwards" they come apart and you have to replace them (for about $200 each). Not sure many tire companies would own up to doing that; most might just claim the tires were "defective" and return them under factory warranty rather than absorb the $800 loss for their own mistake.

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PostPosted: Wed Apr 25, 2018 12:41 pm 
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Location: Derby, CT
IT takes me about 2 minutes to get to the highway. From there, cruising at about 70mph, there is no vibration. After about a few minutes at this speed it starts to build from a low hum to a noticeable rumble coming from the rear of the vehicle. It is not felt in the steering wheel but the mirror will shake somewhat. Without changing speed, after about a minute the noise will start to disappear. My tires are Continental Extreme Contacts in stock sizes. The wheels are fine and have been balanced many times in the past few months. I am fairly certain the problem lies in the rear, either the differential or the Joints. I heading home now. will add more later.

Thanks Guys

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PostPosted: Wed Apr 25, 2018 3:34 pm 
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There is a 3-mile patch of roadway on Rte15 which makes my car rumble and shake until I'm off it. Just a thought.

Well, it sounds like your guys have changed a lot of the "usual suspects" so if you still have the rumble/vibe, it's something you haven't touched yet. Yours is a convertible so I guess we should know whether this happens with the top both up and down? I know some Porsches and the early 350 ragtop and several other 2-seat drop-heads had anti-wind buffer screens behind the driver because certain speeds buffeted your fillings loose.

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PostPosted: Wed Apr 25, 2018 3:54 pm 
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I think I know that stretch on 15 Frank mentioned.

My guess though is that it is still a balance issue, possibly even with your new tires. Do you have different sizes front to back? If same try switching wheels with tires front to back and see if anything changes.

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PostPosted: Thu Apr 26, 2018 6:16 am 
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This morning driving to work it started again then quickly faded out. It's as if lubrication took effect to quiet it down. But just as I was making a long right hand turn in Bridgeport on 95, I heard the rumble start again.

I am going to try to record the sound by placing a microphone in my trunk connected to my camera. This way I have something to show the mechanic. Most of the work I had done to the car was covered under warranty. This was done at Girard Nissan in Groton. I need to check with them to see if a local dealer will honor that warranty so I don't have to drive the car to Groton.

John, the tires are different sizes front to rear. I don't believe it is a balance issue as after the last repair at Girard Nissan, I took the car up to 120mph and there were no vibration and the car handled perfectly. Just had that minor light vibration on warmup. Its that vibration that is steadily getting worse.

As a side note: The tires I bought (continental Extreme Contact) have awesome wet traction. I can put the pedal to the floor in the pouring rain and the car will just grip and go. But I would not recommend them because of the ease of picking up nails in the sidewalls. Twice in the first 3000 miles.

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PostPosted: Thu Apr 26, 2018 8:56 am 
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Yeah, that rumble bothers me too. Probably mechanical, differential, wheel bearings? :roll:

Sounds like the balance is OK then. I am having trouble understanding though why you feel your Conti's would be more prone to picking up nails in the sidewall than any other performance tires. Sounds like you just had bad luck following some idiot in a pickup dropping nails on the road. Some years ago, I had just put brand new tires on my car at Town Fair Tire here in Orange, and within 1/4 mile from the store on my way home (no lie), I ran over a bolt that went right though the tread. I was so pissed I couldn't see straight! :evil:

Good luck on finding out the cause of the rumble and keep us posted on your progress.

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PostPosted: Thu Apr 26, 2018 11:15 am 
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Differential grumbles on turns? Do you have a positraction/limited slip rear?

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PostPosted: Fri Apr 27, 2018 7:59 am 
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Comes standard with Viscous limited slip differential.

This morning I recorded my trip into work. Having reviewed the recording I am more concerned with what is happening. There is a distinct metallic grinding sound even when I think it has quieted down. The drone of the exhaust just covers it up. I now have something to show the mechanic. My guess is this is going to be expensive. Differential most likely.

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PostPosted: Fri Apr 27, 2018 9:24 am 
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Really hard to guess by remote-control (never having heard it), but I wonder if your differential is remaining locked all the time? Do the rear tires ever squeal when you make slow turns? The rear wheels need to turn at different speeds as you turn a corner (inside wheel turns slower than outside wheel, which has to cover a wider radius in the same amount of time). To allow for that, limited slip ("PosiTraction") differentials need to 'release' on turns. If they remain locked up all the time both wheels turn at the same speed on turns, breaking traction and will 'grind' on straightaways. There are also some differential adjustments (such as backlash) which might make weird noises, but usually under acceleration/deceleration, and any of the 3 differential shaft bearings (wheels or driveshaft) might be wearing out. Does the car run straight or does it want to pull to one side? Also, do you get a 'U-joint clunk' when you start slowly or reverse?

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PostPosted: Fri Apr 27, 2018 10:10 am 
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Does the car run straight or does it want to pull to one side? Also, do you get a 'U-joint clunk' when you start slowly or reverse?

The car runs straight and does not pull. No u-joint clunk. I listened again to the sound recording and realize I need to do it again. This time remove all loose items from trunk and place the microphone in the boot to cut down on the exhaust noise. Can't tell what is the exhaust and what is the rumble. I kept at a steady speed (60mph) with the cruise control on. The noise became very loud after a minute. If I can isolate the sound, I will post it somewhere so you can hear it.

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PostPosted: Fri Apr 27, 2018 1:30 pm 
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If you're still accepting comments I'd like to put my two cents in on this issue. Never overlook the fact that a problem might have a simple fix. When you feel this vibration you could try applying pressure with you left foot to the brake pedal while maintaining speed with your right foot and see if the vibration goes away or changes. By lightly applying pressure to the brakes you'll immediately know.. if any of the brake pads are floating/loose and/or vibrating; or if one of the calipers is loose. I've also had a metallic scrapping sound and a vibration coming from (believe it or not) from a rotors dust cover either being bent or vibrating (like a reed in a clarinet for making music). All that I had to do in these instances was to grab the metal "pie dish" with both hands and pull it away from the rotor slightly and another time I put a slight kink/ripple in the dust covers rim with a pair of vise grips which stopped/eliminated it from vibrating.

Rumbling in the rear and then clearing up could be an improperly adjusted emergency brake cable(?) or the slide pins holding the calipers might not have been cleaned and greased properly thereby not allowing one or more of your calipers to "float" freely and remaining in slight contact with the rotor(s) = vibration.

Not knowing the type of noise and vibration that you're hearing and feeling does make it harder for us to try and help diagnose your problem. Is the vibration being felt through the gas pedal, floorboards or through your buttocks and seat? Sometimes something as simple as what I've described will be the fix. Here's hoping that you find the cause soon. Good luck.

Howard

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PostPosted: Fri Apr 27, 2018 2:33 pm 
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If you're daring enough you could try performing this test. :shock: Immediately after driving the car, exit the Z, lick your finger (or dip it in some water or stick it in your water bottle), then put it between any two spokes of your tire rim and try lightly touching the rear rotors :evil: HOT! to see if they are hotter than the front rotors. This would let you know if one or more of the calipers are hanging up/dragging causing your vibration. :wink:

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PostPosted: Fri Apr 27, 2018 3:16 pm 
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Everyone seems to be hitting the logical possible causes. Of course, checking all of these things can be a bit tedious and frustrating. :roll:

On a brighter note, Frank got the number of "goods" right on the subject Beachboy's title song..... I found myself singing it to myself just to check if he had one too many!!! :P

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