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Scary and mysterious diff bolt


PLATA

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I had a light rear noise/clank and to my surprise it was the outer bolt on diff mount that was loose to the point that it came out by hand. That bolt was put tight when a weld was needed on the old Nippon part last summer . >> post-36683-0-89637700-1406384342_thumb.jpg my diff set up . post-36683-0-53395800-1406384559_thumb.jpg the outer passenger side  bolt that was loose . What could be cause to that bolt to become that loose , the former owner never had an issue with the set up  :confused: 

Edited by PLATA
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That diff mount design puts a twisting motion on the four mounting bolts of the cross-member.  The nose of the diff is pulling up on a fairly long lever arm with the four bolts of the cross-member as the fulcrum.  It wouldn't be surprising if the heads of the bolts broke off eventually.  

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I have a Q45/r200 diff on my Z.>>>> post-36683-0-83957800-1406392313_thumb.jpg this is the mount post-36683-0-89621300-1406392219_thumb.jpg that set up give the former owner zero problems with 10K miles during his ownership , last summer a crack on the old Nippon metal part of the custom made mount was repaired post-36683-0-58266000-1406393157_thumb.jpg .. and last week the bolt next to the weld repair came loose. That diff set up has a total of 18K miles, any suggestions in order to avoid future issues.  :idea: 

Edited by PLATA
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You could run two legs from the cross-member up to the old diff strap mount holes.  The diff strap mounting bolts would be in shear and would stop the motion.  Basically a boxed mount off of the cross-member with the two tongues sticking out front to hold the diff nose.  It would be stronger but still puts a bending load on the tongues.  Adding two more legs diagonally from somewhere close to the front of the tongues back and up to the diff strap mount hole areas would help that problem, making the tongues shorter.  If there's room.   As an assembly it might be pretty big and bulky.

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"Somebody" willing to sacrifice a pile of money needs to design a crossmber for short nose diff installation into the Z. It would weld into the unibody and distribute forces into the body correctly. Until that happens, I think we will continue to see these kinds of problems. If you look hard at the tiny tabs that the RT bolts to, you will not bolt it in with total confidence, even with a long nose diff. I'm figuring the Nissan engineers saw these problems, so they put a little motor in the car and cobbled together that crazy busquit and strap contraption that the Z left the factory with. So long as you had 150 hp at the flywheel, at put it to the ground with 5-1/2" tires, life was good. Well, we kinda screwed that up!

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"Somebody" willing to sacrifice a pile of money needs to design a crossmber for short nose diff installation into the Z. It would weld into the unibody and distribute forces into the body correctly. Until that happens, I think we will continue to see these kinds of problems. If you look hard at the tiny tabs that the RT bolts to, you will not bolt it in with total confidence, even with a long nose diff. I'm figuring the Nissan engineers saw these problems, so they put a little motor in the car and cobbled together that crazy busquit and strap contraption that the Z left the factory with. So long as you had 150 hp at the flywheel, at put it to the ground with 5-1/2" tires, life was good. Well, we kinda screwed that up!

:iagree:

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You could run two legs from the cross-member up to the old diff strap mount holes.  The diff strap mounting bolts would be in shear and would stop the motion.  Basically a boxed mount off of the cross-member with the two tongues sticking out front to hold the diff nose.  It would be stronger but still puts a bending load on the tongues.  Adding two more legs diagonally from somewhere close to the front of the tongues back and up to the diff strap mount hole areas would help that problem, making the tongues shorter.  If there's room.   As an assembly it might be pretty big and bulky.

 Mike aka motomanmike ,this looks  like a possible solution and a case of beer  :D 

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How is the vibration in the car? Are the u joints in good shape? As I look at this I am reminded of an issue I had when one of my u joints failed on an old truck of mine. 

 

Good Luck

Edited by AkRev
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Don't tack weld the bolt!  That will cause a loss of torque even though the bolt head does not turn.  The heating and cooling will cause the thread faces to loose friction.  Just install new fasteners correctly per the FSM and use some blue Loctite if it makes you feel better.

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Don't tack weld the bolt!  That will cause a loss of torque even though the bolt head does not turn.  The heating and cooling will cause the thread faces to loose friction.  Just install new fasteners correctly per the FSM and use some blue Loctite if it makes you feel better.

^^^Please listen to John!!!^^^

 

Also, as far as the notion of "nobody has addressed this yet" (paraphrasing), have you looked in the FAQs?  Jon Mortenson did a writeup on this back in 2006...

http://forums.hybridz.org/topic/50499-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount-faq/

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