Bad vibration at 3000 RPM's and up

[stevesLX]

I have a 89 LX.When I get at 3000 RPM's I got a vibration that you can feel thru the whole car. And the faster you go the more louder and worse it gets. I had the driveshaft balanced and u joints are good. Just had the motor rebuilt and they checked the balance with my flywheel and pressure plate. But now they marked for me how my pressure plate should go on my flywheel with 2 yellow paint marks. But I had to get my flywheel turned and the machine shop who turned it removed the yellow marks so I had to just guess how I thought they had the pressure plate lining up on the flywheel. So in a nut shell I just rotated the pressure plate until it lined up on the flywheel and I bolted it down. Now I know its not tires either because I just put new wheels and tires on it the other day and it still does it. At 2500 in 5th gear you start to get this vibration that comes and goes comes and goes. Its like every 1-2 seconds it vibrates and then as your speed and rpms increase it s steady and just gets worse as you increase the speed and rpms. I just rebuilt the tranny. I dont think thats the problem. Unless the main shaft in the tranny is bent a couple thousandths. The only thing I haven't looked at is the rear end. I have no idea at what I would even look for. I dont know anything about rear ends or gears. I know it is a 4.10 and its 5 lug. Couldn't tell you when the fluid was ever changed in it. I know that wont fix it. So any help would be appreciated

 

[6SpeedLX]

check spark plug gap....use nothing but Autolites

 

[stevesLX]

What does spark plug gap got to do with this vibration. Lets be serious now

 

[Badlilstang]

Did they put the alignment pins back into the flywheel to center the pressure plate? Ive seen this happen a few times.. can cause vibes if you dont have those pins in.

 

[stevesLX]

I know when I just threw the pressure pate on the flywheel there were 3 pins that the pressure plate mounted into.

 

[Badlilstang]

Thats them.. Do you get any vibrations when revving the motor when sitting still? Do you have an aluminum drive shaft? Ive gone through a ton of vibe problems so I feel your pain. The pulsing vibe in 5th gears sounds like a driveshaft problem. Ive had my stocker balanced and spicer u-joints installed and still had the same problem. It took an aluminum drive shaft that finally smoothed everything out. If your not getting vibes when just free revving the motor while sitting still then thats a good sign. Those are usually harder and more expensive to fix. Also if your pinion angle is off it can cause vibes as well.

 

[facemelter71]

Hey dont know if itll help but check the fan,dont know if you have a stock fan or flex blade but i had a flex blade that broke a blade off and vibrated like that.Also check the dampener make sure it hasnt slipped or moved.

 

[stevesLX]

I dont have a clutch fan any more just a electric one and I do have a aluminum driveshaft and I had it balanced and the u joints checked. I'm a newbie so bare with me here. You say the pinion bearing and being lined up right.Are you taking the spline that the tranny lines up with in the engine. It may not be lined up right. I dont know. I stuck the motor back in the car, I thru my tranny into it raised up the tranny with a jack and tightened up the 2 tranny tailhousing mounting bolts stuck my drive shaft in and bolted it to the rear exactly how it was when I took it apart and thats it.

 

[Mr Grim]

I believe he is referring to the angle between the tail-shaft and drive-shaft, and the angle between the drive shaft and the rear diff pinion. These 2 angles should be equal and opposite of each other, or close to it. Ie; +4 deg tail-shaft/DS and -4 deg DS/diff pinion. Any angle causes the DS to "lope" as it is turned. By making the angles opposite of each other, they cancel each other out, and remove the lope.
I have a truck with +4 and +4 and I have that same pulsing vibration you describe. Just don't have the time, patience, and cash to fix it right now.

 

[Badlilstang]

Yes to the person above thats the pinion angle im talking about... the big thing is if the car vibes only going down the road vs. vibrating while sitting still.. this will help you eliminate a lot of options. While going down the road when you feel the vibration around 3000 or whatever.. push clutch in and see if the vibration remains... If it does this the vibe doesnt follow engine speed and follows the speed the car is moving which brings in the driveshaft and rearend pinion angles into play. Go free rev the car sitting still and let us know if it vibes or is smooth. Hold your hand on the shifter and bring it up slowly all the way to 5k rpm... if its smooth thats a good sign the motor was balanced correctly and your problem is not there but further down the line.

 

[6SpeedLX]

What does spark plug gap got to do with this vibration. Lets be serious now

in all seriousness, Im Certified by Ford in Noise/Vibration/Harshness....are you?


if the plugs arent gapped right its gonna cause a vibration under load above 2500 rpm....seen it plenty of times....like badlilstang said, try and elimate if its an engine speed concern or a vehicle speed concern...or if it only does it under load or not.....when was the last time the car had a tune up? you said you checked all the drivetrain components and everythings checked out good.....if you can find something with an Electronic Vibration Analyzer and knows how to use it, that would help narrow it down a lot

 

[stevesLX]

O.K. guys for the most part it is smooth there is some vibration but I would say normal just the long tube headers and that that are right underneath me. Its not even close to the vibration that I get while going down the road. Also 6 speed I wasn't being a smart a## I just asked this same question one other time and the one and only reply I got was sounds like you are are running mudders on your car. So you never know. I gapped my plus according to the haynes manual which I beleive was .045. Dont quote me on that but I did use the haynes manual. So all this drivetrain pinion stuff I need some help here how do I accomplish this and get it right and what tools do I need to do it. I aasume the pinion flange is what the drive shaft bolts up to. This is all new to me.

 

[Mr Grim]

Pinion/DS/Tailshaft angle should not be an issue if everything is stock. Does the vibe change when you push in the clutch above 3000 rpm? Does it get worse while accellerating from 3000 up? Let some of the smarter guys (I am not one of them) on here know and they will narrow it down for ya.

 

[stevesLX]

I just drove the car up the street from work real quick and I got up around 400-4500 in 4th gear and it was vibrating and I push the clutch in and it was still vibrating until I slowed down. And yes the higher you get above 2500 the more it vibrates. I am leaving work now and have about an hour commute home I will check back in then hopefully someone can narrow this down for me.







This is just one major problem out of 2 that I have. The other is lifter noise. Just had motore rebuilt 3 angle valve job .005-.007 taken off heads and deck cut down. And low and behold I now have valve train noise that I didn't have before the rebuild and I am at .045 preload. Factory non adjustable pedastal rockers. But that's another subject for another time. I want to get to the bottom of this vibration. It's driving me crazy.

 

[86bluecobra]

where do you feel the vibration? Is it in the steering wheel? Do you feel it in the seat of your pants?

 

[stevesLX]

you feel it throughout the whole passanger compartment so yes in the seat of your pants.

 

[86bluecobra]

Is there any way its a seperated tire?

 

[Badlilstang]

Ok well you know its not the engine being out of balance because it does it going down the road with the clutch pushed in. Like Grim said if the suspension is stock you shouldnt have a pinion problem. Are you feeling it in the shifter real strong? What about your wheels.. any chance of them being bent or off balance? You still have all stock rear control arms? I know this crap is annoying but just stick with it and you will find a solution. The car had no vibrations before the rebuild? During the rebuild was there anything else you chanced? Same tranny mount and crossmember?

 

[Badlilstang]

Is there any way its a seperated tire?

Im wondering if its in the wheels/tires area also... if its a drive line vibe you usually feel it real strong in the shifter.

Hang in there Steve... you will find it.

 

[86bluecobra]

the only other real possibility i can think of is that when your engine was reinstalled it didn't get set in quite right and your exhaust is touching the body somewhere and you car getting the vibration that way but i would still think tires.