GT out of balance?
 

I have a '95 GT, stock engine, 5 speed 138k miles and I am running out of ideas for this problem: there seems to be something out of balance (or at least it feels like it) when the engine revs between idle and 1000 rpm and under wide open throttle past 4200 rpm. It is a large vibration that rattles the stick shift and the body of the car with force.

The engine does not miss or exhibit any other mulfunction and runs strong, but it feels as if something is going to fly out of the engine compartment or underneath the car at any second. The vibration is evident when the car is not in gear (neutral) or moving, so I am thinking that the drive train is not the issue...

I have checked the vacuum lines for leaks (none found), replaced the distributor housing, replaced the spark plug wires with Ford Racing parts and switched to a MSD coil - no change.

Your expert opinion is appreciated before something does fly out or I toss the engine in the river... HELP and thanks!

have your driveshaft checked for balance.

If it is, buy an aluminim from ford, ~$180.

Just throwing this out, but since you mentioned you notice it when it's not in gear. Have you checked your motor mounts? You might have a bad one.

I thought about the shaft and it is on the list for upgrade, but since it happens even when not in gear maybe the motor mount idea is closer to home...

Doyou think there could be a problem with the crank dampner or the flywheel?

Two comments...
1. If you buy a FRPP aluminum driveshaft plan on having it balanced. I have two of them, both needed to be rebalanced. The shop where I took it had seen over 100. Im still happy I went with it though.
2. When sitting in neutral, does the vibration occur less with the clutch pedal depressed?? If so you have either a bent input shaft or a misalignment between trans and flywheel (very common with scattershields, less common with cast bellhousings).......

Thanks for the heads-up on the shaft...

I'll check the difference with the clutch engaged... I know things are running pretty thin down there too

It looks like i am reaching that magical point were all parts are going to scream for replacement - I think my wallet is screaming too

Check your timing w/ a timing light, and see if the TDC mark on the balancer is off. If it is, the balancer may be separating. You should further confirm this by comparing the rotor (pointing to #1) and the TDC mark.

Take care,
~Chris

I had the same problem and it turned out to be an out of balance Centerforce clutch...i'd imagine it could happen with a stock clutch though also.

Now thats interesting. I had a problem with mine while using a Centerforce clutch. Just assumed the clutch was balanced. How did you happen to discover that it wasn't balanced.......

I called Centerforce and they sent me a new one...changed it out...and the vibration went away. With those weights they use on the pressure plate (to add more force on the clutch disc) they were saying it is pretty easy to get one that is out of balance, especially if it got dropped or something during shipping.

Now I'm really interested. Had a bad vibration above 3k. I assumed it was the scattershield out of alignment. Spent 3 days messing with that and finally gave up (went with a standard bellhousing). I replaced the Centerforce clutch and the vibration improved but didn't disappear completely. Guess I'll see if I can find anybody locally that can rebalance it. Thanks for the info......

Thanks for the input guys... I know that the clutch is on it's last leg, but the comment from PKRWUD about the balancer is disturbing.

I thought it was a large chunk of steel shaped and positioned to balance the crankshaft rotation that was pretty much imbebbed into the crank assembly - so i took a look at it and it shows slight scraping marks, as if it is or was touching something at one time or another. If it is "coming apart", can it be replaced or retorqued without taking the engine apart? what do you recommend as the next step?

Thanks and sorry for the time off the list... vacation was calling!

Whoa! I'm starting to have a similar problem in my 95 GT. Only my problem is not RPM related. Mine is speed related. It seams every time I hit about 90 mph I start to get the same vibration, worse as I go faster. I don't normally drive that fast so I don't know when it really started.

Shakes the living sh*t out of the shifter too.

I would assume mine is drive line related. I guess I should get up to that speed and depress the clutch and see what happens. I was thinking either drive shaft or something in my rear gears (I have them changed to 3.73's and whenever work is done to a car and you have a problem....)

Any ideas for me?

You can try unbolting the driveshaft from the yoke, rotate the driveshaft 1/4 turn and then bolt it back up. This is Ford's standard procedure for reducing driveshaft vibration....

other causes could be loose fly wheel or pressure plate bolts and i would definately check the balancer for seperation don't keep driving it until you figure out what is wrong otherwise you may be fixing a much larger problem.

The balancer is not hard at all too change. Take the fan and shroud off. Remove the bolt from the center of the balancer that holds it to the crankshaft. Then don't forget to remove the washer. Attach the puller, if you don't have one, you can probably borrow one from a parts house, and remove it. When re-installing it, DO NOT HAMMER IT BACK IN. Use the bolt to sinch it back down. It only goes on one way. There is a notch in the balancer and a pin on the crankshaft. Put some RTV in the groove. Put your fan, belt, and shroud back on and test drive.
Caymon

Thanks for the latest suggestions - as 'biglockcoupe' suggested I have not been driving it at all for fear of bigger damage.

I'll try unbolting the balancer and check for damage/looseness... Since it is just a hunk of metal, it seems unlikely that it would fail - maybe it is coming loose or the bolt is failing.

Good suggestions as always...

Thanks!

When I changed my timing chain I noticed that the rubber between the inner and outer peice of the balancer was starting to come out of place. I replaced the balance with a stock replacement and noticed a considerable reduction in vibration.

It's two pieces, not one.

Take care,
~Chris