Frustration with drive line vibration - Vintage Mustang Forums

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post #1 of 19 (permalink) Old 06-19-2017, 09:42 AM Thread Starter
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Frustration with drive line vibration

Hi,

Replaced the u-joints on the drive shaft, tightened loose bolts on trans mount both on trans and on frame. Still have vibration from @60 -80. I know the passenger rear wheel bearing needs to be replaced, as it makes a little noise. I haven't checked motor mounts yet, but plan on it. Tightened the front wheel bearings and greased them.

Not sure what this can be. Could it be the rear end being loose inside? I don't think its a wheel balance issue. The steering wheel doesn't shake.

Any help appreciated.

Thanks,
Perry

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post #2 of 19 (permalink) Old 06-19-2017, 09:59 AM
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is it in the front, or the rear? Worse during acceleration, deceleration, or constant? When occurring, does it continue or stop if you kick it into neutral? Are you sure the wheels are balanced 100%? Has it always been there, or did it just come about- if so, what did you change recently? If the wheel bearing is bad and you know this- replace it first, then reassess the situation.

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post #3 of 19 (permalink) Old 06-19-2017, 11:14 AM Thread Starter
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Thanks for the reply. I believe it to be in the rear, or centralized, if that makes sense. The steering wheel does not shake like a front wheel out of balance of bad front end. It occurs under acceleration as well as deceleration. It's between 60-80. I put it in neutral and it's still present, back in gear it seems to reduce slightly. I don't think it's always been there, at least not as far as I recall. It's my sons and I don't get to drive it very often. I had the transmission rebuilt a few years ago, but that shifts fine, no noise. I marked the drive shaft when I took it out to replace the transmission. I may try to switch that to see if there's a difference. I am also going to check motor mounts. It doesn't seem like tire imbalance, but I'll have to check that as well. The passenger rear wheel bearing is suspect as I can hear it, so I will replace.

Thanks,
Perry

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post #4 of 19 (permalink) Old 06-19-2017, 11:22 AM
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With that, it does sound rear end/driveline related. Did you mark the yoke to shaft for orientation when you replaced the joints? I'd pull the shaft and recheck the joints just to make sure a needle didn't roll over on you. Make sure they rotate smooth and freely. If that's all good, I'd still replace your wheel bearing first, but you could swap tires front to rear to see if the shake moves with them. That would be a cheap easy way to check the balance- short of just taking them to a shop anyway. Given that it's your son's car, you may just raise it up and spin the wheels to check for a bent wheel. That's how my Dad caught me years ago... twice

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post #5 of 19 (permalink) Old 06-19-2017, 11:24 AM
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I just ordered a new drive shaft. I changed up a lot of parts (suspension, motor & tans mounts, etc.). So, the one I ordered was actually slightly longer than the original.

The guy told me when I measured that even if I was a 1/4" off on my measurement that it could result in vibration at high speeds of 60-70mph.

Did you change anything up recently like suspension or drivetrain mounts, etc?

Matt
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post #6 of 19 (permalink) Old 06-19-2017, 05:50 PM Thread Starter
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Thanks for the replies. I will swap tires all the way around to check that. I can put it back on jack stands and rotate tires too to check for a bent wheel. I did manually rotate the drive shaft after install and they rotated fine. I am tempted to change the orientation on the rear end of the drive shaft to see what it would that would do.

No other changes to driveline or suspension. It's got the same drive shaft as we got it with. I did have the transmission rebuilt a few years ago, but that seems fine. At speeds up to 50, no trouble. Funny thing was, the trans mount bolts to the frame as well as the ones from the trans to the mount were loose. I thought tightening those might eliminate the vibration. I am going to check motor mount too.

It needs rear springs, and could use shocks all around, but those wouldn't have any effect I don't think. It doesn't seem to be wheel related, but I'll check.

Its been so long since we got it and I don't drive it very often, I don't recall when this cropped up. I haven't changed anything else on it.

Thanks,
Perry

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post #7 of 19 (permalink) Old 06-19-2017, 06:58 PM
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I had exactly the same issue years ago. It drove me nuts looking for the solution, tried everything. Turned out the rubber inside the tranny mount had degraded badly, but was hard to tell with a visual inspection. Popped a new mount in, and no more vibration. Worth a try.

Cheers.
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post #8 of 19 (permalink) Old 06-19-2017, 10:13 PM
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A harmonic at higher speed (over 50) that comes, then goes, usually is a tire.

Bart

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post #9 of 19 (permalink) Old 06-20-2017, 12:49 AM
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Another thing to check are the yokes on the driveshaft. I had the same issue where I'd pick up a vibration at about 70mph. Figured the driveshaft needed balancing, so took it to a driveshaft repair guy in Tucson. He took a look at it and showed me the rear yoke was worn out. He twisted the rear u-joint through it's normal rotation and the bearing caps rotated along with the u-joint. He told me it was a definite sign of the yoke being worn out. I replaced the driveshaft with a newer aluminum one out of an Explorer and the vibration went away. The u-joints on the original driveshaft were Moogs that were only a couple years old, and I don't do any burnouts, hard launches, etc.



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post #10 of 19 (permalink) Old 06-20-2017, 07:54 AM
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How can you tell if a motor mount is broken?

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post #11 of 19 (permalink) Old 06-20-2017, 08:38 AM
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Quote:
Originally Posted by IndyFive-O View Post
How can you tell if a motor mount is broken?
The easy way- start the car, put it in gear, HOLD THE BRAKE FIRMLY, and 'goose' the gas pedal. By that I mean from idle, rev the engine up just a bit, then back to idle. With the hood up, or better yet using a second set of eyes, watch the engine. If the mount is bad, the engine will actually 'flop' up and down on the mount. You'll see an obvious excess of movement from it. Do the same in reverse to check the other side mount. Another method- put a wide block of wood under the oil pan on a jack and raise the engine slowly- watch the mounts to see if they separate. (BTW- the 1st method is more fun)

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post #12 of 19 (permalink) Old 06-20-2017, 09:18 AM
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Quote:
Originally Posted by gt350sr View Post
The easy way- start the car, put it in gear, HOLD THE BRAKE FIRMLY, and 'goose' the gas pedal. By that I mean from idle, rev the engine up just a bit, then back to idle. With the hood up, or better yet using a second set of eyes, watch the engine. If the mount is bad, the engine will actually 'flop' up and down on the mount. You'll see an obvious excess of movement from it. Do the same in reverse to check the other side mount. Another method- put a wide block of wood under the oil pan on a jack and raise the engine slowly- watch the mounts to see if they separate. (BTW- the 1st method is more fun)
Manual trans so the "fun" way is a no-go. The oil pan is up to being pushed on like that?

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post #13 of 19 (permalink) Old 06-20-2017, 09:22 AM
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Quote:
Originally Posted by IndyFive-O View Post
Manual trans so the "fun" way is a no-go. The oil pan is up to being pushed on like that?
It actually would still work- just 'goose' the clutch pedal out with the brake applied and engine idling. Probably be a good idea to chock the wheels to be safe.
Yes- the wood block is what will protect the oil pan- just make sure it's a wide thick piece. Alternately you could use an engine hoist and a lift plate or chain bolted to the heads, but that's a lot more work.

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post #14 of 19 (permalink) Old 06-20-2017, 07:34 PM
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My 67 had a vibration and I took the driveshaft to a shop, when they tried to balance it the rubber inside it had deteriorated so it couldn't be balanced. They made me a new shaft and now all is well.

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post #15 of 19 (permalink) Old 06-20-2017, 11:41 PM
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I'm confused - rubber inside of a drive shaft? I thought they were hollow tubes.
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