Bad Vibration at 55 mph. Whats up?

[Sick03Vert]

For some reason my car has a serious vibration issue going on at around 55 mph. The whole car shakes and just feels real "unstable". I took the car to the tire shop and they couldn't find any flat spots on the tires. I had them rebalance everything and they told me all four were way out of spec. However, even now I have the same vibration. Guys, its so bad that it has created rub marks on the side of the drivers side dash from the door panel rubbing. It's ridiculous. Car does not pull like its an alignment issue. I know the verts have a lot of chassis flex, but should it really be this bad? Also, there's something up with the front end. For one, I get the creaking, slight popping noise when turning the wheel at a complete stop left or right. Similar to what my 03 Mach 1 did and I never found the problem. But the big issue is when you are moving in reverse, it feels like the front axle is ready to fall off. I mean, it "thuds" as its rolling and turning the wheel either way while moving in reverse really makes it worse. I would really like to figure this out. I'm not one to complain about creaks, rattles, whatever. But this is on my nerves.

Thanks for any suggestions! :beer:

 

[Blueline]

Check your front end, bushings in control arms, steering rack, and also wheel bearings. Also, dont rule out the tires. I know you said they were rebalanced, I chased a similar vibration but around 80mph and my steering wheel would shake up and down. I had 2 different shops rebalance the wheels. Everytime I brought them back they said they were out of balance. This was with brand new tires on them too, finally got a mechanic who took his time road force balancing them and they came out perfect.

First start by checking wheel bearings, bushings in the front end and the rear end. GL!

 

[MoKo_03SVT]

it definitely isnt normal...vert or not. my cobra is also a vert, and i have never experienced anything like you are describing, since owning it.

did the car just all of this sudden start doing this? or has it always done this, since you've owned it? are you sure its never been wrecked?

 

[Sick03Vert]

It's done this since I've owned it. It has a clean Carfax and Autocheck, but you and I both know that doesn't mean anything except it hasn't been wrecked AND reported. :nonono:

I work at a GM dealer (I know) and I've been thinking about having them put it through a thorough inspection like we do the cars we buy and sell.

I'm not a mechanic or know-it-all by any means, but I do have tons of experience with Mustangs and looked this car over very carefully before I bought it. Checked for all the usual stuff, the usual mods, etc. and thought it was clean. I'll be very disappointed if it turns out I got screwed. :fm:

 

[Tims97SVT]

It sounds like a suspension problem if the wheels where rebalanced. Have your work go over the suspension. Then go from their.

 

[Bdubbs]

Could a inbalanced driveshaft or the big halfshaft nut being loose cause this?

 

[SVTgsxrdude]

i would check the drive shaft. i had an old ford that did the vibrating thing at 50 turned out the drive shaft was bent... you couldn't evan see it till a machinist put it on a lathe

 

[hotcobra03]

start back with the basic`s,,,

is vib only at 55mph?

can you make vib change at 55mph by doing anything? on/off clutch,,,on/off gas,,,in gear/in neutral...

we all have friends with mustangs,,,try switching all 4 wheels to rule out tires before spending any more money...

 

[Sick03Vert]

Thanks for all the replies!

I will be checking to see if any actions I take at 55 (clutch engaged/disengaged, downshift, upshift, etc.) make a difference. I will let you guys know what I find out.


I ran another Carfax on it. It came back no wrecks and, as I was told, lists me as just the second owner of the car. So that's encouraging. I will also see if I can borrow a fresh set of rubber for about half an hour to do some testing.

Again thanks for the replies!:beer:

 

[GSPsnFORDs]

It could be the driveshaft but could it possibly be the U-joints? I haven't read much on here about the u-joints going bad on these cars so I'm just guessing. I'll say this though, I'm on my 3rd F150 and you know when a u-joint goes out...you can hear it, and more so in reverse. However, my gf's Pathfinder had a bad vibration between 45-55mph which felt more like the front wheels being out of balance. Had them checked and re-balanced and still had the problem. My next thought was alignment so I had the dealer check that and everything else. Turned out to be a rear u-joint that was bad (no "syptoms" like my trucks had previously). Might want to check those first before going to extreme measures. Just my thoughts....

 

[Blueline]

Im going to go with suspension, wheels bearings or still wheels. If it was the driveshaft he would feel the vibration in all the gears at different speeds. For example, if hes feeling it in 6th gear at 55mph. 1500rpm, he would feel the vibration in 2nd at say 3000rpm because the driveshaft is at the same rpm.

Get the car up on some jack stands and check your wheel bearing and suspension like I mentioned earlier. It will rule out alot or the prob. may be obvious. GL!

 

[ACMUSTANG]

"I get the creaking, slight popping noise when turning the wheel at a complete stop left or right" --- alot of that could be in the ball joints, lack of grease or a bad one. thorough front end check like everyone else has stated

 

[Blueline]

Also bud, if they didnt road force balance the tires, they may have not picked up the flat spots. Just another thought.

 

[Sick03Vert]

Well I had a chance to road test the issue today. The vibration is from 55mph to 65mph. It does this whether the car is in gear or in neutral. However, if you put the car in neutral and coast, the problem resolves itself by the time it coasts down to around 50 or so.

I have tried driving the car with different amounts of throttle at different speeds, and it seems the 55 - 65 window is the only time this is an issue. Quick starts from a dig do not bring it on in low gears and crusing at 70mph, you'd never know there was a problem.

I'm trying to get some jack stands so I can get up underneath and have a look. I will update as I rule out each item or hit more questions.

I also want to check for flat spots myself....these tires were on the car when I bought it so there's a chance that could still be the issue.

Thanks for the replies! I really appreciate it. I'm getting a good sense of the direction I should be looking in. :beer:

 

[Blueline]

My flat spots were bad enough that with the car jacked up I spun the front wheels I could actually see the flat spot while I spun the wheel. I could see something wrong with the tire just spinning it by hand

 

[hotcobra03]

55-65 in 6th is a low rpm vib....can you get the same vib feel if ,when sitting still in neutral,and hold rpms around 1600-1800...


how about at speeds higher than 70...i have a bad tire on my rear that does shake like a bitch on front,but on rear you only feel it above 70,,,texas as you know 80 is slow

 

[Sick03Vert]

Well I finally had a chance to pull the wheels off the car. And I found that the drivers side front seems to have a bit of a flat spot. As someone said, I could see it just by spinning it in the sunlight. So that may be the whole issue. Guess I will pick up a replacement and see what happens. :nonono:

Thanks for all the advice. Will update once tire is replaced later this week. :beer:

 

[ds98formula]

so what was the verdict??

 

[Liquidsnake]

Check your wheel bearings, and rear axle nuts. Also one time I had a rear axle pinion nut back off a little bit(crazy), and it caused a vibration. Pull the drive shaft out and rotate it 90 degrees and re-bolt it in.

Generally a tire out of balance is a consistent vibration from low speed all the way up, not an intermittent. A flat spot possibly.

Rear axle nut torque is 250/ft lbs I believe.

 

[brian97cobra]

if the rear diff bearings are worn and you have to much back lash you will get a nasty vibration.