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Help Needed: 06 Dogbone Bolt Shear - Engine Mount issue?

1968 Views 6 Replies 3 Participants Last post by  SoCal
Hello Fellow New Beetle owners.
This is my first post. We bought an 06 New Beetle Convertible used from a relative. I knew the car had not been super-well cared for, but it was offered at a great price and I figured it would be okay. Well - there have been several issues that now have me concerned.

The car had the feared borg warner transmission clunk issue - but the prior owner did not tend to it within the warranty period so I found a local shop and had it repaired properly. Tranny is now great.

Fast forward to about 6 weeks ago when my daughter had an issue with the car - the v-belt came out of track and the car locked up. Further investigation found that the bolt that secures the dogbone from the subframe to the transmission had sheared off - - so the engine was able to move too much - causing the belt to come out of track.

I was able to remove the sheared bolt and replace it with the Stretch bolt I bought from the dealer. All seemed well

about 6 weeks of driving and - lo and behold - same exact problem.

I'm wondering:
1- could the motor mounts be too "soft" - - allowing the engine too much movement, which is causing the bolt shear?

2- Should I install a stronger/harder (e.g. 12.9) 10mm bolt to try to address the shear issue?

3- Should I consider replacing the motor mounts too?

Note that at this point I'm probably over-invested in the car - - given the tranny and some other items I've had to repair - - so going in and doing the motor mounts is not exactly something I'm keen to do - - esp since it might not resolve the problem for sure...

ANY advice / guidance is greatly appreciated.

Other fyi:
I'm in SoCal - Los Angeles area.

The car was previously in the desert - -Palm Springs. Thinking maybe the high heat would contribute to premature motor mount breakdown???
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When you had the transmission repaired, did they replace the transmission mount stretch bolts with new ones? If they reused the stretch bolts maybe some of the bolts have failed.
Hi -
Thanks for your addition to the post.

The bolts for the transmission were all replaced with vw stretch bolts. Seems solid.

When I removed the prior (sheared) bolt, I replaced it with a VW stretch bolt (head stamped 8.8).

I had to remove the dogbone at that time (to get clear access to the broken bolt) - so I actually replaced all the bolts with new stretch bolts.

Now I am going to remove the recently-sheared bolt and I am replacing it with a hardened bolt (grade 12.9)

We'll see how things go from here....

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Hmm. Sounds like you are troubleshooting this methodically. Is it possible that the torque wrench that you used to torque the stretch bolts is a little off, and caused the stretch bolts to be overtorqued? Besides the motor mount, that's the only other thing that I could think of.
That's a good thought. I used the air wrench at my friend's shop (he has a lift - what a relief!) - - but for this next re-install I'm going with my old-school torque wrench that I know is calibrated.

Should be making the repair over the weekend - will keep you posted.

Appreciate the suggestions-
The Pendulum support(dog bone) bolts on the transmission end are 40Nm 30 ft pounds

Support to subframe end 20Nm 15 ft pounds
Thanks for that!
I'm planning to swap in the new dogbone / bolts tomorrow.
Will let you know how it goes.

Appreciate the inputs.

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