# Vibration



## DarrelH (Nov 18, 2006)

I am new this board and the new owner of a 1990 2+2 5-speed manual. The car has 57K miles and is like new. It has a vibration on the seat of the pants between 40 and 50 mph. It is always there, clutch in or out, in or out of gear. It does seem to get better the longer I drive on each trip. Any help isolating this problem would be greatly appreciated. Thanks, Darrel


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## Zen31ZR (Mar 24, 2004)

Could be several things, including an improperly balanced wheel or a driveshaft balance weight fell off or a loose bolt back by the differential....... 

You should do some experimentation, such as what speed it seems to disappear or if it simply gets worse the faster you go. Also if it makes the steering wheel shudder slightly, or if it's only felt through the seat. Seat only vibrations are typically a driveshaft problem.


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## DarrelH (Nov 18, 2006)

Zen31ZR said:


> Could be several things, including an improperly balanced wheel or a driveshaft balance weight fell off or a loose bolt back by the differential.......
> 
> You should do some experimentation, such as what speed it seems to disappear or if it simply gets worse the faster you go. Also if it makes the steering wheel shudder slightly, or if it's only felt through the seat. Seat only vibrations are typically a driveshaft problem.


Thanks. It is definitely not on the wheel - seat only and most noticeable between 40 and 50 MPH. The vibration lessens with longer drive times.


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## DarrelH (Nov 18, 2006)

I should have added that the tires are new and wheels balanced - problem continues.


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## Z_Rated (Apr 29, 2006)

First off congrats on the new ride and welcome to the boards. If you think you might need some help look up ProjectZ, it's a local Phoenix area car club, cool people too. Also, for parts and advice give Concept Z Performance on 7th Ave (I believe, not street) South of Camelback a call. Honestly, it's hard to say what may or may not be your problem, but steering wheel usually means up front and seat of the pants the rear. Good Luck, Z


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## DarrelH (Nov 18, 2006)

Z_Rated said:


> First off congrats on the new ride and welcome to the boards. If you think you might need some help look up ProjectZ, it's a local Phoenix area car club, cool people too. Also, for parts and advice give Concept Z Performance on 7th Ave (I believe, not street) South of Camelback a call. Honestly, it's hard to say what may or may not be your problem, but steering wheel usually means up front and seat of the pants the rear. Good Luck, Z


Thanks for the info. I first bought this car in 1992 and sold it in 1999 to my daughter who garaged it for 8 years. Now I have it back. I'll try to contact projectZ or Concept Z Performance.


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## Zen31ZR (Mar 24, 2004)

I suppose it could be one of the 1/2 shafts out back has a problem. Sometimes if they sit for a while the grease hardens and can bind it up. If its worn out one of the balls inside can split and the piece migrate elesewhere and create an out of balance vibration. One slightly loose bolt on the U-bolts for the driveshaft can do that as well. I'd get the rear end inspected if you don't want to do this yourself. Its basically just jacking up the car and going under there to move things around and see what they do. The rear of the car must be partially off the ground, to unload all the suspension components back there. 1/2 shafts should have no vertical or horizontal movement except in line with the shaft. The drive shaft should have no movement at all from the rear. The wheels themselves can have a tiny bit vertical movement, this test is mostly to determine if any of the wheel bearings are worn out. Also push and pull on the rear struts from all directions possible, to make sure of no loose mountings. Check the brake rotor vents to make sure there is no dirt in them. This has the same effect as an unbalanced rear wheel. I can't think of anything else right now , but somebody else might...... Be carfeul when doing this yourself. Use jack stands and if you have an extra wheel laying in the garage, put it under the edge where the jeck point is.


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## Z_Rated (Apr 29, 2006)

Wow, sitting for eight years? You have a lot of inspecting to do my friend. Wheels would of been my first guess, but you stated they are new so I guess what Zen31ZR stated stands to reason. In addition, check for signs of leaking/leaked fluids and areas of rust on moving parts around suspension components since you say it seems to get better the longer you drive. Original shocks? if so I'd be surprised if they are still in good working order after being idle for so long. Where about in town?


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## DarrelH (Nov 18, 2006)

I"ll get it in the air this week and see what I can see. Thanks. I don't know of a good shop for this car in the area so will probably have to solve this myself.


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## Z_Rated (Apr 29, 2006)

There is one shop that specializes in the Z32 that I know of, but I have not used them myself. If and when you contact Concept Z and go there for parts you will also be at that shop! Convenient ehh? It's Pitstop Performance. If you use them post up about the service.


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## Spongerider (Nov 18, 2002)

DarrelH said:


> I should have added that the tires are new and wheels balanced - problem continues.


So your problem occured right after your tire change?


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## Z_Rated (Apr 29, 2006)

I'm understanding it as it was a problem before and after the tire/wheel service...


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## DarrelH (Nov 18, 2006)

Z_Rated said:


> I'm understanding it as it was a problem before and after the tire/wheel service...


The problem was there before and after changing the tires. I drove the car about two years ago and the problem was there then. It didn't just sit. It was driven about 15K miles in 7 years. The owner had a driver car, the Z, and a motorcycle and not much time to play - also northern climate. I think someone asked where I am located. I'm on the west side in Estrella Ranch.


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## Zen31ZR (Mar 24, 2004)

Could also be something as simple as a bent wheel. Sometimes these tire places don't watch when the wheel is on teh balancer machine. It has a hood over it anyway, so unless you are specifically watching the wheel , you won't see it wobble. And such a wheel can be balanced, as far as the machine is concerned. The machines only account for vertical anomalies, a change in vertical weight as the tire rotates, not horizontal.....


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## Z_Rated (Apr 29, 2006)

DarrelH are you on the factory stockers? The original wheels and sizes? Reason I ask is I might be able to get you some to try on your car to see if that makes a difference. I was the one who asked, I'm on the West end as well. Z

BTW, anything else you have overlooked, forgot to mention or were not clear on from your first post? Any accidents? How long ago was the tire/wheel service and what exactly was done? Run anything over? Scrape the underside on a speedbump or steep curb/driveway? Not trying to be an ass, but it could be easier/faster to possibly resolve your issue rather than have you keep clarifying specifics post after post.


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## DarrelH (Nov 18, 2006)

Z_Rated said:


> DarrelH are you on the factory stockers? The original wheels and sizes? Reason I ask is I might be able to get you some to try on your car to see if that makes a difference. I was the one who asked, I'm on the West end as well. Z
> 
> BTW, anything else you have overlooked, forgot to mention or were not clear on from your first post? Any accidents? How long ago was the tire/wheel service and what exactly was done? Run anything over? Scrape the underside on a speedbump or steep curb/driveway? Not trying to be an ass, but it could be easier/faster to possibly resolve your issue rather than have you keep clarifying specifics post after post.


The facts as I know them.
Vibration at 40 - 50 MPH (not felt in steering wheel) (speed sensitive, not RPM sensitive) Gets better after driving for several miles, but doesn't go completely away. Car has had this problem for at least two years, maybe longer. It was thought to be tires because it would "go away" after driving a distance and the car did sit for weeks (months?) at a time. This car has not been in any accidents since early 1992 - don't know about before that. It has not been abused at all - no rough roads, curb hopping, etc.. Suspension is original, wheels are original. Tires are about 3 months old (less that 1K miles). Replacing tires and balancing made no difference in vibration. 
Plan of attack.
I will rotate front wheels to the rear to see if vibration goes to the steering wheel. I don't think it will.
I will lift the car and inspect for play in the center drive shaft bearing , u-joints, and/or axles. I have heard from others that the center bearing or a frozen U-jointwill cause this vibration. One person recommended installing a 1-piece drive shaft.
If I don't see anything during inspection, I will take it to a dealer or maybe the shop referenced above. I don't mind paying to have it fixed, but I am tired of getting ripped off (paying to have cars fixed and still having the problem or even new problems after spending hundreds of dollars).
If you want, you can send me an email and we can meet up sometime.
Thanks for all of the input.
Darrel


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## Spongerider (Nov 18, 2002)

DarrelH said:


> The facts as I know them.
> Vibration at 40 - 50 MPH (not felt in steering wheel) (speed sensitive, not RPM sensitive) Gets better after driving for several miles, but doesn't go completely away. Car has had this problem for at least two years, maybe longer. It was thought to be tires because it would "go away" after driving a distance and the car did sit for weeks (months?) at a time. This car has not been in any accidents since early 1992 - don't know about before that. It has not been abused at all - no rough roads, curb hopping, etc.. Suspension is original, wheels are original. Tires are about 3 months old (less that 1K miles). Replacing tires and balancing made no difference in vibration.
> Plan of attack.
> I will rotate front wheels to the rear to see if vibration goes to the steering wheel. I don't think it will.
> ...



Can you tell if the vibration is coming from the front or back of the car? Sorry if it's already been stated.


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## DarrelH (Nov 18, 2006)

Spongerider said:


> Can you tell if the vibration is coming from the front or back of the car? Sorry if it's already been stated.


I would say it is the rear. Can't feel it on the steering wheel.


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## Z_Rated (Apr 29, 2006)

I would hold off on the one-piece and do the rotation first. Visual check for flat spots and any irregularities while rotating and then road test. From there I would go to suspension and drive-train, hopefully if after the rotation there is no change it should narrow it down to front or rear, that's no cost. If there is a change and you want a loaner wheel let me know. 

Friday I think I'm helping a local do some suspension work. I'll ask what he wants for the old OEM parts, but I think it's a TT. Are you free Friday, good time to meet and check things out? Time is set for early/mid afternoon.

p.s. Check your private messages DarrelH


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