Vibration at 90 MPH

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74DartSwinger360

74DartSwinger360

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Rear end starts to vibrate at 90 mph and before that it howls from 2500-3500 rpm. Rear has been completely rebuilt and no un usual marks on the gears. the line is straight up the middle of the gears. Does anyone know what this could be?
Thanks
 
If you changed ratio it's most likely the shaft.

As for the line, is it in the middle on both sides, and if so is this a cheap gear or china copy cat company gear.
What ratio did you go from and to.

Without lots of detail for this when it starts, it gets worse, it goes away after ___ mph.... this is like walking up to your bank teller and not saying a word and expecting her to know wth you want.

.
 
"rear end howls at rpms" doesn't make any sense to me.
Spin balance machines dont turn the tires that fast. They dont compensate for the balance of drums, etc.. either. You would have to have it speed balanced to get perfect.
 
jack the car up put it in gear with someone in the seat let the wheels turn and see if the wheels and tires are running true.I had a bent axle flange on mine do this...........Artie
 
If it is a gearset howl, does the rear howl under acceleration or decceleration? If it howls while one or the other occurs it is likely a gear noise.
Vibration usually doesn't occur from gear noise (howling), likely some other source. I would look at what changed from your gear swap. Did you do something with the driveshaft? Is there a tight U-joint? Maybe the yolk on the rear is worn or spread so the drive shaft is not running centered to the yolk? Are your old gears still set-up on a pumpkin? try putting those back in. Just my thoughts
 
There's a number of things that could cause the vibration. Start by rebalancing front and rear tires. Then check the pinion angle. Maybe then axle bearings. Possibly a bad set of gears. Been there done that.
 
Sounds like you have 2 issues that are unrelated. The howl is most likely due to an improperly set up gear set. The vibration, well like the others said it can be a few things. Bad tire(s), bent wheel, driveshaft out of balance, bent axle, etc...

74DartSwinger360 said:
The rear is straight as an arrow.
Click to expand...

How did you determine this?
 
340duster said:
If it is a gearset howl, does the rear howl under acceleration or decceleration? If it howls while one or the other occurs it is likely a gear noise.
Vibration usually doesn't occur from gear noise (howling), likely some other source. I would look at what changed from your gear swap. Did you do something with the driveshaft? Is there a tight U-joint? Maybe the yolk on the rear is worn or spread so the drive shaft is not running centered to the yolk? Are your old gears still set-up on a pumpkin? try putting those back in. Just my thoughts
Click to expand...

Has original gears it came with from factory I only added a suregrip. And howls at accel and when holding the same rpms
 
A frozen brake caliper can add a really bad vibration too.
 
fishy68 said:
Sounds like you have 2 issues that are unrelated. The howl is most likely due to an improperly set up gear set. The vibration, well like the others said it can be a few things. Bad tire(s), bent wheel, driveshaft out of balance, bent axle, etc...



How did you determine this?
Click to expand...

It was checked when I rebuilt it years ago. and has always howled. Has new tires. Straight rims.
 
when you get off the gas the vibe is gone, not a trace of it, or it is there but not as pronounced as when under cruise or accel?
 
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