View Full Version : Unbalanced or bent drivshaft?

09-03-2002, 04:43 PM
Does anyone know the symptoms for an unbalanced or bent driveshaft? A friend of mine says my driveshaft is either bent or out of balance.

How can you tell?

The symptom’s are, it resonates real bad at 60-70Mph, about 2800-3300Rpm. It’s so bad that you can hardly talk to the passenger at these speeds. I had always thought it was exhaust droning. My keys that are hanging from the ignition start vibrating at this speed as well. The droning has a pattern to similar to small propjet aircraft at cruising and almost as loud!

Now, I’m NOT sure this is the problem. It doesn’t eat U-joints and I’ve always thought it smoothed out at higher (100Mph) speeds. Either that or I’ve tuned it out!

How much does it cost to balance a driveshaft?

09-03-2002, 05:03 PM
Hey BrianU, It sounds like it could be out of balance, but if it is that loud I am suprised it hasn't done damage to other parts of the drive train. I don't think it is too expensive to get a driveshaft balanced maybe $100 or less. I've never had to get it done so I am not sure, maybe someone else can help with this.


09-03-2002, 05:41 PM
my ex wife was good at balancing a drivesh-------- awe, you get the picture.

dirty dan
09-03-2002, 06:13 PM
How do you Know it is the drive shaft?
Have you done any tests to confirm this?
I would would put a jack under the back andput it on jack stands.
Then leaving the front down.
Pull the drive shaft out.
If youleav the rear up the fluid will stay in the trans.
Start the car put it in drive and runit up to 60 -70.
If the vibs are still there then its not the drive shaft or the rear.
If the vibes are gone then the drive shaft or rear is the problem.
I have had new drive shafts made useing the original ends.
For about $70 including ballanceing.
Or you could just replace it with a used one.;)

09-03-2002, 06:57 PM
It could be any number of problems. It could be caused by the drive shaft, a wheel bearing, the ring & pinion, pinion angle (most common to this problem), internal to the tranny, etc.

Mach Manny
09-04-2002, 02:12 AM
where can you feel the vibration?

If it feels like the lumber support of your seats is vibrating, this typically is an imbalance in your rear wheels, while unbalanced front wheels seem to transmit their vibrations through the steering wheel and also in the floorboard. Front ends that are out of alignment are felt only in the steering wheel (death wobble), shot body mounts are felt in the floorboards and seats, and transmission/motor mounts are see in the physical shaking of the motor at a resonant RPM.

Hope this helps.

09-04-2002, 02:01 PM
Note the RPM that the vibration is persisting in. Then drive the car in a lower gear at the same RPM. If the vibration is gone then it is a speed related problem that is most likely to be with the driveshaft or rear pinion.

I have the same problem. I now have a brand new driveshaft which revealed a slight vibration at 40 mph and a large vibration at 75. However, the growl form the rear end is telling me that the rear pinion bearing is probably toast.

09-05-2002, 05:39 PM
Well, I crawled under there last night and started checking the transmission mount, ok, the weights on the driveshaft, ok, pinion angle, looks ok! Then I looked at the yoke on the third member and the driveshaft universal joint. The universal joint was “offset” in the yoke! That didn’t look right to me so I called a friend of mine. He told me that can’t happen because the “C” clips hold the universal joint in the center of the yoke. Well that would be true if you were not missing a ‘C” clip on one of the cups! The other “C” clip on the opposite cup was turned so the open end was against the yoke. Bottom line, the universal joint wasn’t centered. Now that will cause a vibration!

I unbolted the shaft and pressed the cups on tight and centered it. Problem resolved! I can cruise quietly (Relative term!) at 60, 70 or 80 now with no v

09-06-2002, 10:48 AM

I had the same fricken problem on my car. I tried new U-joints then after inspecting it looked like the rear joint wasnt centered in the yoke. Did a real careful "eyeball"job and the problem was resolved! I thought those things were idiot=proof, but i guess not!


09-06-2002, 03:09 PM

I was knid of hoping they were idiot proof, if you know what I mean! :rolleyes:

09-06-2002, 04:42 PM
Brian, Thats great that you found the problem. However I would do one other thing..

It sounds like you just reset the exisiting u-joint.. while it may be working fine now, I would wager that it has had some damage done and wont last as long as it should.. I would recommend installing new u-joints in the drive shaft.. I think you would be doing yourself a favor in the long run...


09-06-2002, 05:44 PM

I agree, I'll probably be slapping in a 4.10 for the Houston Mopar show next month. I'll swap it out then.