I need help, 30, 60 mph vibration....ARRRRGGGHHHH!

[soctty7676]

98 GT Conv 17" factory wheels - I have got a vibration that shakes the whole car. Comes through the seat, steering wheel, shifter, etc... and if you hold it at 60mph long enough you start to feel sick from the vibration. From what I can tell, it almost looks like the rear end is jumping up and down, but I can only see it through the rear-view mirror and maybe that is what's vibrating. This vibration is always at 30-35 & 60-65 mph no matter what gear/engine speed and does it with the clutch in/out.

Anyways, to try and fix this I have replaced 4 tires with Fulda Extremo's and put 30psi in them (balanced twice), new clutch, new driveshaft, and 1 wheel (old one was slightly bent). The guy who replaced the clutch looked at all suspension components, didn't notice anything out of whack. He recommended some special tire balancing procedure that costs $100 (he doesn't do it and didn't recommend anyone, so I think he really believes in it). I am tired of spending money on this stupid crap, I could have put a PI intake/head conversion kit on the da*& thing for what I have spent so far.

One thing that concerns me is the right rear wheel/tire has 2 big weights on it after they balanced it last time. Maybe the tire is out of round or something?? Supposedly the $100 balance job takes this into consideration.

If anyone has any ideas, I would greatly appreciate it!
Scott

 

[Chopper1]

Raise the rear of the car and set it down on jackstands.Chock the front tires front and back to prevent any movement.Have a trusted friend get in,start the car and run it up to the speed that the vibration starts and see what's shakin'.Look to see at idle whether there is a jump in the tread of one of your tires.I read somewhere that drive shafts are balanced with the slip yoke as a set and you should use the new parts together.Repost and tell us what you find.

 

[soctty7676]

Raise the rear of the car and set it down on jackstands.Chock the front tires front and back to prevent any movement.Have a trusted friend get in,start the car and run it up to the speed that the vibration starts and see what's shakin'.Look to see at idle whether there is a jump in the tread of one of your tires.I read somewhere that drive shafts are balanced with the slip yoke as a set and you should use the new parts together.Repost and tell us what you find.

Make sure the car is facing out of the garage right? Ha ha, my luck it would jump off and end up in my spare bedroom.

So do I put the jackstands under the rear axle, or the body?

 

[Chopper1]

Personally,i'd use the body because the vibration could shake the car off the stands if put under the axle.Plus this will allow the vibration to show itself easier.

 

[mr. jones1]

I am just offering some other things to look at.
has the car had any height changes that would affect pinion angle?
is the trans mount good and the right one?
is the bushing at the rear of the trans in good shape. This is a sleeve that I believe to be pressed into the tail housing. If this sleeve is badly worn it makes the drive shaft flop around.
That tire you mentioned with alot of weights-usually the tire shop can rotate the tire on the rim and avoid using so many weights.
A simple items would be very bad/blown shock,, once the tire starts bouncing your in for a nasty ride.
I have had similar problem on other cars and it is a royal pain sometimes to find.

 

[soctty7676]

Well, I never got around to jacking the rear end up this weekend. Had too many other things going on.

BUT, after mentioning my problem to my neighbor, he said maybe it is because the rear end isn't level. I looked, and sure enough, the right side of the rear sits lower than the left.

What causes this? I checked all the bushings and made sure all control arms and stuff were tight. I can't see anything that looks out of whack. Could this be because of a blown shock absorber? I tried springing the rear, but it is so freakin stiff, it doesn't even hardly bounce down at all.

 

[crazynorwegian]

it could be that one of your shocks have seized. there easy to disconnect, just take off the bottom bolt, and you should be able to push the shock up and it will compress if its working properly. the balancing procedure the mechanic was talking about is called ride matching. we had a machine at my old shop that would do it. it will reduce the amount of weight on the wheel, but I dont think that is your problem.

 

[mr. jones1]

sounds like a broken coil spring. If you disconnect the shocks you will be able to
move the springs and verify both. springs hold up the car, shocks control bounce.

 

[soctty7676]

sounds like a broken coil spring. If you disconnect the shocks you will be able to
move the springs and verify both. springs hold up the car, shocks control bounce.

This makes sense because I can turn right and the car stays fairly level, but when I turn left, the car seems to really lean into the turn (already checked swaybar, looks ok), and if I hit a bump turning left, I hear noise coming from the right rear.

I had to replace the right rear wheel because it was bent, had a flat spot. I bet the previous owner hit something bending the wheel and breaking the coil and/or blowing the shock.

I will have to take it apart this weekend and see if I can find anything.

Thanks all!
Scott

 

[soctty7676]

Ok, I took the rear wheels off and inspected the springs and shock absorbers. The springs don't seem to be broken, but maybe I don't know what to look for. I took the bottom bolt off of the shock absorber and inspected the spring. Looks like its all together, I don't see any breaks or anything. I also pushed up on the shock absorber and was able to "bottom it out" fairly easily. Is this right? Car's got 85,000 miles and I think they are the original shock absorbers.

So, while I was at it I rotated the tires to see if the bounce would go to the front of the car. Nope, still shaking through the seat, so I am almost positive it isn't a tire issue, something in the rear end is messed up. The car leans to the right in the rear. Could this be a shock absorber issue? Probably need to be replaced anyways.

Thanks for all your help!
Scott

 

[mr. jones1]

the shock is tired if it has 85000 miles on it but it does not affect
ride height. if the spring is not broken I don't know what else to look for
concerning ride height.
Look again at the back wheels/axle you may have a bent axle.
If you jack the rear of the car up (tires off the ground) run it in gear as listed before and you see the wheel wobble you ether have a bad wheel, axle or both.

 

[urban96]

ya might be a bent axle

 

[03MustangGT]

That sounds like a problem I had on my 96 Exploder, I mean Explorer. The car would vibrate pretty hard while being driven in "Drive" and "Overdrive" but in lower gears it wouldn't. Also, if I were on an uphill slope, shifted into drive, and then hit the gas, the car would drift back like I were in neutral, and then it would all of a sudden drop into gear and I would move forward. If I remember correctly, there was a crack in the driveshaft or a tube that surrounded the driveshaft or something like that. I ended up just getting a new transmission. Im not saying this is your problem, but it's what happened to me

 

[soctty7676]

Ha, exploder, that's what I call mine all the time. I bought a brand new Eddie Bauer back in 2003....It is the biggest piece of crap vehicle I have ever owned. It is in the shop more than I can drive it. I tried to turn it in for the Lemon Law, but the Ford Rep took advantage of my ignorance and I got screwed out of that. They pretty much stalled until my 24 months were up. Oh well, I will wait till I'm right-side up on it and get rid of it. Unfortunatly, this vehicle is why I will NEVER buy a new Ford again in my life.

Well, put new shock absorbers on the rear, I am going to do the front this weekend. It helped, but the vibration is still there. I think the shock absorbers are just helping absorb part of it now. It did make quite a difference on the way the rear of the car rides now! It also drifts a lot better now, I did a u turn and nailed it and did a perfect slide!

Do I have to have the front end aligned after changing the front struts? I just had it done, I would hate to have to do it again. The manual didn't mention it, but it is a cheapo Chilton.

 

[soctty7676]

Update!

Well, out of my depression of not being able to fix my vibration problem.....I ordered a Flowmaster American Thunder cat-back system from JEGs. I am tired of spending money trying to eliminate the problem, so I will just try and cover it up!

 

[propellerhead]

Quit driving on railroad tracks!

-just kidding!

 

[mr. jones1]

if you change front struts you will need to align it again.

 

[soctty7676]

Good news! I replaced the front struts (now all four have been replaced) and the wobble/vibration has seemed to dissappear. It may be that the new shock absorbers are absorbing it now, but in any case, the car doesn't shake around and drives a lot better! It's amazing the difference it made as far as the way it handles and absorbs bumps in the road.

Thanks for all your help! I may still jack the car up and see if something seems out of round or anything because I find it hard to believe bad shock absorbers would cause the car to shake around like it's tires were out of balance.

 

[mr. jones1]

glade to hear things are looking up.
Just be careful when you put the car up and verify axles/wheels.

 

[magnum347]

Check your U joints. They may be bad and will cause nasty vibrations.