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  #1  
Old 08-20-2003, 08:04 AM
YO7_A66 YO7_A66 is offline
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wow Vibration @ 70 mph

I currently have a vibration in my 70 Challenger 340/727/489 that shakes the fenders and the hood around 70 mph along with a droning type of noise. I have read many of the past "vibration" threads and I have checked several items (k-member bolts, sway bar bolts, wheel hubs are flat and new outer wheel bearings, tranny mount, new tail shaft bushing, drive shaft has been balanced with new uv joints) on the car due to those posts. Now I have some results that I wanted to see if I could get some feedback on.
Last night, I checked the drivetrain angles and they are very close to being flat. Using a digital protractor, I took the next numbers and rounded them off to the nearest .1 degree.
My tranny housing is currently at .7 degrees upward, my pinion is setting .6 degrees down, and my drive shaft is at .5 degrees. One of the previous threads said that NAPA sells the "rear axle castor wedges". With the above angles, it appears that I have a 1.3 degree angle and with a street driven car with leaf springs, do I buy the 4 degree wedges to get me into the 5-7 degree area?
Thanks
Dave
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  #2  
Old 08-20-2003, 08:57 AM
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cuda66273 cuda66273 is offline
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Your Garage floor needs the wedgies...the tranny should be 3* down the same angle as the crank.....

Take your measurements from the tailshaft mount surface it should be 3* if the floor is 0*.
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Old 08-20-2003, 09:40 AM
YO7_A66 YO7_A66 is offline
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wow

I will shim down the tranny tailshaft tonight to get the 3 degrees and then check my anlges again.

Thanks for the reply.
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Old 08-20-2003, 02:07 PM
YO7_A66 YO7_A66 is offline
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wow

Any ideas why my pinion seal is leaking after I had a mechanic replace my 3:91 gears to a new set of 3:55's? He replaced them last Fall and ever since then the lube has been leaking from the seal. I gave him a new seal, crush sleeve, and the gears for the install. The rear had no leaks before the gear swap.
Could the above vibration have anything to do with the pinion? Is the leak a "hint" of something else that might be bad?

Thanks
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Old 08-20-2003, 02:38 PM
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6 packin 6 packin is offline
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I have found that most driveline vibrations are due to the driveshaft. Try rotating it 180 deg then road test it. Is this the orignal driveshaft? Has it been cut? I dont care who balances it it still might not be correct. I had the one in my car balanced by the People at Dana Spicer Driveline services, it wasnt done corectly. Actually they shorten it and welded it up. Put the car on jack stands and make sure its safe, pull the car in first gear and let it idle, pull the emergancy brake untill the tires are only spining maybe 1-2 revolutions per second then crawl under it and look at the Yoke and U-Joint where it meets the driveshaft. You will see if its out of round. This is kinda dangerous but it can be done safely. There should be no wobble at all.
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Old 08-20-2003, 04:37 PM
b-1ken b-1ken is offline
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Could also be bad tires. The 2001 Dodge Ram that I recently bought had a noise that sounded just like bad wheel bearings. I put all new tires on it (6) and it is as quiet as new. I can't imagine a 3 degree change in the drive shaft angle would cause the fenders to shake. The drive shaft in my '88T-Bird Super Gasser is not dead on and that shaft spins at 7000 + rpm!
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Old 08-20-2003, 05:08 PM
YO7_A66 YO7_A66 is offline
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wow

6packin: I have had the drive shaft company by a very popular drive shaft company in Indy about 2 months ago. There was no difference before or after the balance. Thanks.

b-1ken: The tires/drums are next on my list after the pinion angle is fixed. I have had all the tires/wheels balanced last fall with no change in the vibration though. this time I do want to see if the tires are all "round".
The 3 degrees will actually be 6 degrees, 3 in front and then I need to match that in the rear. Thanks.
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Old 08-20-2003, 08:23 PM
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Will the vibration go away if you increase the speed or is it too bad / dangerous to try? And did you do any thing to the car just before this started? Hit a curb, pot hole, change tires, etc etc?
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Old 08-21-2003, 12:22 AM
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1972roadrunner 1972roadrunner is offline
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i had a bad vibration in my rear end at high speeds as well that 'droned'....my pinion angles were fine, and still, it vibrated. well, in my transmission's class, my professor wanted a real life sim, so i towed (no motor) my car to the shop at the college. turns out, i had about 1/8" of play in my pinion!! had it been driven any more, i would have had to get new gears. the torque on the pinion was all wrong, and it had 0 inch pounds of drag torque.

we took it apart, inspected all bearings/races, cleaned everything, and put it back together. we tightened untill the correct drag torque was obtained, and when i drove it the other day (motor running), NO VIBRATIONS!! err, well...i DO need new u-joints as they're beginning to go out, but no noticable vibration.

especially since the pinion seal is leaking, pull the driveshaft off the rear end, and see if the pinion will move foward and back at all. jack up the rear, take the tires off, and see how hard it is to turn the pinion. it should have (i think) around 15-25in/lbs of drag torque.

good luck!
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Old 08-21-2003, 07:57 AM
YO7_A66 YO7_A66 is offline
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23T: The car runs real smooth up until 65-70mph. I did not drive it over that but at that speed the shaking was not huge, just annoying. Thanks.

1972roadrunner: I have pulled side/side on the pinion with no movement. I will check to see if it will pull/push. With the car in the air, I can turn the pinion by hand, but I will get an adaptor and see if I can get my "/lbs wrench on it. Thanks.

I started on shimming the tranny last night and found that when I zero'd out on the concrete floor that the tranny was angled down -1.5 degrees. I only had time to try 1 shim adjustment and got it to +1.5 degrees. I will get back on it tonight until I get the 3 degrees.

Thanks for everyones replies.
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  #11  
Old 08-21-2003, 08:28 AM
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cuda66273 cuda66273 is offline
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Check the rpm at the vibration point and then bring it up to the same RPM in 1st and 2nd and see if you have the same vibration. This will tell you if it's an engine or driveline vibration.
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