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Carl Jensen
Experienced User
Username: carl_jensen

Post Number: 31
Registered: 2-2005
Posted on Thursday, 17 December, 2009 - 04:48 am:   Edit PostDelete PostView Post/Check IP

A week ago I started to hear a grinding noise from my Shadow's rear end. It turns out that the final drive torque arm was scrunched and rubbing on the drive shaft (you can see the rubbing on the attached photo right next to the large round cutout).

The forward rubber bushings for the arm are in good shape, and the bushings on either side of the crossmember were replaced a while ago. The crossmember itself looks to be in good shape and the prior owner had the strengthening modification completed on both sides. In addition, the torque arm does not appear to have been attached to a tow chain and I have never used the arm as a jacking point.

Does anyone have an idea what may have caused the torque arm to fail? I have a new one on the way at a cost of just under $700 and would like to avoid a repeat of this problem.

Any advice would be appreciated.

Thanks,
Carl

Scrunched Torque Arm 1975 Shadow
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Omar M. Shams
Frequent User
Username: omar

Post Number: 97
Registered: 4-2009
Posted on Thursday, 17 December, 2009 - 04:58 am:   Edit PostDelete PostView Post/Check IP

My guess would be that you picked up some debris from the road with the propshaft (like a gunny bag or a jacket/blanket etc) that got wrapped up around the prop shaft and that caught the torque arm and bent it. The thing you picked up probably shredded itself and fell off after the event.
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David Gore
Moderator
Username: david_gore

Post Number: 923
Registered: 4-2003
Posted on Thursday, 17 December, 2009 - 12:27 pm:   Edit PostDelete PostView Post/Check IP

Certainly looks like impact damage from an external object.

Any possibility of accidentally hitting a speed hump or reversing into a parking space wheel stop barrier?
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 504
Registered: 6-2006
Posted on Thursday, 17 December, 2009 - 06:53 pm:   Edit PostDelete PostView Post/Check IP

Possibly jacked up on it a while ago and has finally failed through metal fatigue at the damaged area?

Valet parking? :-(

Somebody trying to winch the car while it was locked in park.

Changing from a forward gear to reverse before the car had stopped moving?

Putting it in Park while still rolling but on a steep incline?
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Carl Jensen
Experienced User
Username: carl_jensen

Post Number: 32
Registered: 2-2005
Posted on Friday, 18 December, 2009 - 08:50 am:   Edit PostDelete PostView Post/Check IP

Thanks Omar, David and Paul for your observations. Based on your comments, it looks as if this was a one-time occurrence, so I feel much better although my wallet is much lighter.

Thanks again,
Carl
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Carl Jensen
Experienced User
Username: carl_jensen

Post Number: 33
Registered: 2-2005
Posted on Tuesday, 29 December, 2009 - 12:20 pm:   Edit PostDelete PostView Post/Check IP

Wow - what a happy ending! My Shadow has always had a vibration on acceleration, and all of my attempted fixes (switching the half-shafts, replacing u-joints, balancing the drive shaft, adjusting the standing height) never solved the problem. But now that I have replaced the torque arm there is no more vibration when I accelerate.

It appears that the torque arm may have been bent all along and had thrown out the geometry enough so that it caused vibrations on acceleration. I guess that the arm finally gave up the ghost due to severe fatigue, but what a wonderful surprise to have the vibration disappear!