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trying to identify driveline vibration at higher speeds...
#1
so I was really paying attention to the vibration in the car, and I'm a bit stuck....

when I approach 59-60mph on the throttle, my rear louvers start vibrating like crazy.  if I ease off the throttle it stops.  to get the louvres to vibrate seems to require a combination of speed 59mph+ and being on the gas pedal....

recently I've replaced the suspension( springs, and shocks) control arms etc.  I have also had a computerized alignment and wheel balance completed.  The car tracks dead straight at highway speed.  the vibration is only minimally being transferred through the steering wheel, so it seems its in the back end somewhere.

at first I thought it was the wind causing just the louvers to vibrate, but now I'm pretty sure its something in the driveline, like the driveshaft being out of balance, but not sure how to explain the vibration going away at speed, but off the throttle.

any ideas?  thanks
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#2
First choice would be u-joints on the driveshaft. Do you hear a clunk or ping when going from forward to reverse?

Other option is tire balance. If you go above 60, does the vibration go away.

1) If the steering wheel is shaking it is the front tires,.
2) If the body/seat is shaking without the steering wheel, it is the rear tires or u-joints.

My bet is the u-Joints

kcmash
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#3
funny you should mention a clunk....I do get a clunk sometimes when changing speed quickly....good call. I've been thinking about that clunk....
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#4
+1 on the u-joints being the most likely. If it's not the u-joints let us know, we'll run through other options.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#5
maybe the rear diff also causing vibration? I just looked at its pretty crusty, and has a decent size leak in the seal. I'm going to change the rear diff anyway, might be a full rebuild...
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#6
If the ring or pinion gear were severally pitted they could be the cause. The pinion bearing is also a possibility, due to the pinion seal leak. A pinion seal leak is often caused by a bad pinion bearing.

I would start with u-joints, though, start with the simple and work your way up.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#7
runninpony 
(08-12-2019, 12:18 PM)MustangNJ Wrote: so I was really paying attention to the vibration in the car, and I'm a bit stuck....

when I approach 59-60mph on the throttle, my rear louvers start vibrating like crazy.  if I ease off the throttle it stops.  to get the louvres to vibrate seems to require a combination of speed 59mph+ and being on the gas pedal....

recently I've replaced the suspension( springs, and shocks) control arms etc.  I have also had a computerized alignment and wheel balance completed.  The car tracks dead straight at highway speed.  the vibration is only minimally being transferred through the steering wheel, so it seems its in the back end somewhere.

at first I thought it was the wind causing just the louvers to vibrate, but now I'm pretty sure its something in the driveline, like the driveshaft being out of balance, but not sure how to explain the vibration going away at speed, but off the throttle.

any ideas?  thanks
Sorry, no idea but if I were to guess...U-Joints!
About your alignment...can you please post the print-out or at least the specs where they set it to? Thanks!

71-73 Mustangs never die, they just go faster!
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#8
NOT A T5 Wrote:
MustangNJ Wrote:so I was really paying attention to the vibration in the car, and I'm a bit stuck....

when I approach 59-60mph on the throttle, my rear louvers start vibrating like crazy.  if I ease off the throttle it stops.  to get the louvres to vibrate seems to require a combination of speed 59mph+ and being on the gas pedal....

recently I've replaced the suspension( springs, and shocks) control arms etc.  I have also had a computerized alignment and wheel balance completed.  The car tracks dead straight at highway speed.  the vibration is only minimally being transferred through the steering wheel, so it seems its in the back end somewhere.

at first I thought it was the wind causing just the louvers to vibrate, but now I'm pretty sure its something in the driveline, like the driveshaft being out of balance, but not sure how to explain the vibration going away at speed, but off the throttle.

any ideas?  thanks
Sorry, no idea but if I were to guess...U-Joints!
About your alignment...can you please post the print-out or at least the specs where they set it to? Thanks!
Here is a good thread on alignments. Post 16 has what mine ended up being set at and I am very happy.

https://www.7173mustangs.com/thread-alignment-specs?highlight=alignment

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
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#9
And yes. U-Joints most likely the cause. I was having the exact same issue, right around 60 would start vibrating in my seat and the rear view mirror was difficult to see out of. Replaced both u-joints and double checked driveline angle. Solved the problem.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
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#10
I had a vibration at around 60 and it ended up being the transmission mount. It was really old and coming apart. I’m sure the others are probably right about the ujoints though, especially if you are hearing a clunk. But something else to check, plus they are really inexpensive, about 10 bucks. Good luck!

run_horse Run Horse Run!
John 72 Q Code
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