Re: Rear axle shim install?
[Re: GoodysGotaCuda]
#2737566
01/28/20 11:43 PM
01/28/20 11:43 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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What angles are you showing? full or part time vibration?
live every 24 hour block of time like it's your last day on earth
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Re: Rear axle shim install?
[Re: RapidRobert]
#2737601
01/29/20 06:51 AM
01/29/20 06:51 AM
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Joined: May 2005
Posts: 4,869 Florida
BDW
OP
master
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OP
master
Joined: May 2005
Posts: 4,869
Florida
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Seems to be part time, hard to tell, but it gets really bad above 65mph. I’ve had the the tires and driveshaft balanced twice, with no difference. Here’s where I started, but have since shimmed tranny up so it’s now 2 degrees down. Again no change, so next step is to shim rear end down 3 degrees.
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Re: Rear axle shim install?
[Re: GoodysGotaCuda]
#2737637
01/29/20 10:24 AM
01/29/20 10:24 AM
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Joined: Dec 2007
Posts: 18,165 Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,165
Mass
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I've slept since this, but wouldn't you want to nose the diff up 2° so that each yoke is in a parallel plane? You want the driveline angle and the pinion angle on parallel planes ON ACCELERATION, a lot of variables determine how much the pinion rotates upward on acceleration, can be upwards of 5 degrees
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Re: Rear axle shim install?
[Re: BDW]
#2737660
01/29/20 11:59 AM
01/29/20 11:59 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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& you want the angles to be minimal. Yes the pinion will rise & how much depends if it is a DD or driven hard. I had a part time vibration & it turned out the yoke was not far enough into the trans. A slightly longer shaft fixed it.
live every 24 hour block of time like it's your last day on earth
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Re: Rear axle shim install?
[Re: moparx]
#2737691
01/29/20 12:44 PM
01/29/20 12:44 PM
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Joined: Mar 2011
Posts: 3,171 Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,171
Michigan
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Overdrive transmissions have no impact on the prop shaft speed.
In third or overdrive at any given vehicle speed the prop shaft turns at the same speed in either gear. Engine speed is lower in overdrive than in third, that’s the benefit. Not shaft speed.
Last edited by Transman; 01/29/20 12:52 PM.
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Re: Rear axle shim install?
[Re: A727Tflite]
#2737717
01/29/20 01:42 PM
01/29/20 01:42 PM
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Joined: Dec 2007
Posts: 18,165 Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,165
Mass
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Overdrive transmissions have no impact on the prop shaft speed.
In a way they do... most production driveshafts are generally balanced for 3000-3500 rpm, when you add an overdrive transmission along with let's say a 4:10 rear gear, .... a .64 overdrive is now capable of moving the vehicle to a speed of 140-150 mph with engine rpm being the limiting factor, prop speed is now extremely high, one of the reasons most aftermarket overdrive suppliers balance the shaft to 10,000 rpm
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Re: Rear axle shim install?
[Re: A727Tflite]
#2737928
01/29/20 11:41 PM
01/29/20 11:41 PM
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Joined: Dec 2007
Posts: 18,165 Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,165
Mass
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Please read my post again - “at a given vehicle speed”.
No arguement that going faster makes the prop turn faster. Agreed, I was making a case for the possible need to look at the driveshaft balance, to rule out possible harmonics Mike
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Re: Rear axle shim install?
[Re: GoodysGotaCuda]
#2737943
01/30/20 01:03 AM
01/30/20 01:03 AM
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Joined: Jan 2003
Posts: 1,908 Nebraska
4406bbl
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,908
Nebraska
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I've slept since this, but wouldn't you want to nose the diff up 2° so that each yoke is in a parallel plane? This is what works for me, every time light load at highway speeds. It would not be the best for a drag car. I am suprised that with the rear at zero and trans 2 down you have an issue, it should be fine, like almost perfect under light load. Is the dana offset left or right, and is engine/trans straight in the car? Just wondering if you may be getting an offset induced vibration.
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Re: Rear axle shim install?
[Re: DAYCLONA]
#2738052
01/30/20 12:11 PM
01/30/20 12:11 PM
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Joined: Sep 2003
Posts: 20,235 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 20,235
north of coder
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Please read my post again - “at a given vehicle speed”.
No arguement that going faster makes the prop turn faster. Agreed, I was making a case for the possible need to look at the driveshaft balance, to rule out possible harmonics Mike agreed, no matter what speed, the tire/rear gear combo will be turning xxxxrpm. however, more than once, i have found deep gears and a short tire has caused driveshaft vibrations because the shaft was only balanced at a somewhat low speed. balancing the shaft at a high speed cured the vibration issue. just putting this out there as something else to look at if the vibration continues after fixing the driveline angle[s].
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