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Check your CV bolts !!
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BrickFan
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PostPosted: Sun May 01, 2011 4:35 pm    Post subject: Check your CV bolts !! Reply with quote

I was under my van today and noticed by chance that a couple of the bolts holding the CV to the transaxle on the drivers side were sticking out! Shocked
Turns out that 3 of them were broken off at the flange and the other 3 were finger tight.
They gave me no notice, no clicking noise or anything. If I had not been under there doing something else, the CV would have fallen out within a couple days.

Just posting this as a reminder. Before you start the summer camping season, take a few minutes to check the bolts holding your CV's in place. It might save you some trouble and $$.

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speedtek
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PostPosted: Sun May 01, 2011 5:07 pm    Post subject: Reply with quote

any chance you've replaced your cv(s) recently or in the last couple years?

Odds are the old bolts were reused if they were.
Most VW's call for those bolts to always be replaced with new (they're a one time use, stretch bolt), if they weren't and the old ones were reused, they can be prone to snappage when torqued or at some point down the line.

It's unlikely that new bolts, properly torqued, would ever have this issue.
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randywebb
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PostPosted: Sun May 01, 2011 5:46 pm    Post subject: Reply with quote

does VW specify 12.9 bolts?

if so, a lower grade may have been used
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chojinchef
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PostPosted: Sun May 01, 2011 6:03 pm    Post subject: Reply with quote

Happy I caught this thread, I have my tranny out for seal and clutch replacement and I would have reused the bolts not thinking any worse of it.

Now I will procure me a new set.

Merci beaucoup.
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BrickFan
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PostPosted: Sun May 01, 2011 6:20 pm    Post subject: Reply with quote

I have had the van for 3 years and have never touched them.
They were all marked "INDRA 12.9" and I was able to get the broken off stubs out of the flanges easily, just turned them out with my finger.
I have had CV bolts loosen up on my syncro van before and I caught them before they broke because I heard the tell-tale click-clack of the loose CV knocking around back there.
These were on a 2wd and never made a sound that I could hear (it's a diesel and quite loud so I might have missed it). All of the other 3 CV mounting areas were tight.
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randywebb
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PostPosted: Sun May 01, 2011 6:43 pm    Post subject: Reply with quote

gotta say INDRA sounds like some chick from India who is not bolted together as well as a German...


dunno much re VW CV setup but I assume it is similar to the setup on old Porsche 911s

there, the bolt does NOT carry shear forces (unless something is wrong) - the bolt clamps the two metal surfaces together and the surface to surface contact area carries the shear force (rotational force, torque, yada yada)
- OCD level use of brake cleaner and Q-tips is often required to get them clean

a common mistake on 911 CVs is to allow some tiny bit of grease to be on the bolt threads or in the female threads in the body of the CV assembly

a 2nd problem is that the naive often do not re-torque the bolts after 100 miles of use

3rd problem is using incorrect bolts, that are not 12.9 in strength

the bolts on the 911 CVs do not need to be replaced each time (and I am surprised to hear that re VWs as usually only stretch bolts need to be replaced each time)
- but the Schnorr washers DO NEED to be replaced each and every time

I have not done this task on my VW yet, nor have I read the Bentley procedure or looked for TSBs from VW on the matter, so YMMV
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Mundopacheco
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PostPosted: Sun May 01, 2011 6:48 pm    Post subject: Reply with quote

...and when you do replace them, don't go back to the 'allen' style, go to the triple square. These are much harder to strip when removing...The usual vendors carry these.
Miguel
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speedtek
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PostPosted: Sun May 01, 2011 10:11 pm    Post subject: Reply with quote

randywebb wrote:


the bolts on the 911 CVs do not need to be replaced each time (and I am surprised to hear that re VWs as usually only stretch bolts need to be replaced each time)
- but the Schnorr washers DO NEED to be replaced each and every time

I have not done this task on my VW yet, nor have I read the Bentley procedure or looked for TSBs from VW on the matter, so YMMV


I wouldn't say for sure this is the case with the vanagon (I know my Audi UrS6 uses ones that can be reused), but they do look like bolts that have been sheared from being retorqued. I know on all mkI to mk3 golfs that one time bolts were used. Btdt on my old rabbit and I actually had to reuse a set temporarily one year until the new ones came in. Fortunately I had a few extra lying around because at least two of them snapped when I went to torque them down.
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AtlasShrugged
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PostPosted: Mon May 02, 2011 5:07 am    Post subject: Reply with quote

Be sure and use a new set of schnorr locking washers too. They get lost with the plates that fit under the CV bolts. The dreaded PO.

Use a torque wrench and as others have said..re-torque at 100 miles.

The washers are available from your favorite vendor or here:

http://www.schnorr.com/safetywashers.html
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PostPosted: Mon May 02, 2011 7:47 am    Post subject: Reply with quote

These are a 12.9 fastener. This is NOT a torque-to-yield application, meaning no need to replace every use.

(TTY would specify torquing to a set value and then turning an additional number of degrees; if you don't see such a spec in the book, they are not TTY)

Torque to the specified values and recheck after some time in use if you want to insure there are none loosening. It is loosening that will lead to shearing off of bolts as the OP experienced. As stated by randy, and in other applications such as this, the rotational shear forces are borne by the friction between the members, said friction is maintained by the bolts in tension. Lose that friction and the bolts bear the shearing forces, which they are not meant to do.
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Wildthings
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PostPosted: Mon May 02, 2011 9:52 am    Post subject: Reply with quote

33 ft*lbs, the Vanagon spec is about 75% of the proof load if the threads are dry.

http://www.cncexpo.com/MetricBoltTorque.aspx

Yield load is 10-15% higher than proof load for a 12.9 bolt.
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insyncro
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PostPosted: Mon May 02, 2011 11:32 am    Post subject: Reply with quote

On my personal vans I use brand new bolts and washers sourced from McMaster Carr.
http://insyncro.wordpress.com/2009/05/15/grade-12-9-cv-bolts-and-washers/
I paint the heads red, as I do with all fasteners that get RED Loctite.
Heat is needed to remove them!
I have not had one loosen unless by me.

dylan


Last edited by insyncro on Mon May 02, 2011 11:47 am; edited 1 time in total
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danfromsyr
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PostPosted: Mon May 02, 2011 11:36 am    Post subject: Reply with quote

How do you apply heat inside the rear trailing arm cave?

usually a recheck on the torque is all that's necessary 50~100miles after install or service. like an aluminum rim.. use a cotton swap to clean the threads, but it's far from perfect.

I've had a few fall off over my 20+ years, but usually were the ones that didn't get retightened.


insyncro wrote:
On my personl vans I use brand new bolts and washers sourced from McMaster Carr.
http://insyncro.wordpress.com/2009/05/15/grade-12-9-cv-bolts-and-washers/
I paint the heads red, as I do with all fasteners that get RED Loctite.
Heat is needed to remove them!
I have not had one loosen unless by me.

dylan
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insyncro
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PostPosted: Mon May 02, 2011 11:50 am    Post subject: Reply with quote

danfromsyr wrote:
How do you apply heat inside the rear trailing arm cave?


Thanks to AlaricH:

http://www.theinductor.com/index.php?m=5&s=0&d=5&ds=0&prod=11

Worth every penny when you have limited space to work in and don't want to torch an entire area.
Very elegant tool, no it aint cheap.

dylan
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randywebb
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PostPosted: Mon May 02, 2011 11:54 am    Post subject: Reply with quote

no need for Loctite - if I did use it (and I did Loctite every bolt, nut, etc. on an old Bus I beat all over the Oregon outback in the 1970's), I'd use blue

another trick is to put nail polish (assuming you can find an Oregon woman that uses it) on the bolt head and over onto the mating surface - easy to see if it has moved

be SURE you inspect all the threads and the wrenching feature on the head of the cap screw (it is illegal to call them bolts in Oregon) - use a magnifier if you need to
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insyncro
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PostPosted: Mon May 02, 2011 12:01 pm    Post subject: Reply with quote

randywebb wrote:
no need for Loctite


I have converted vans with nearly 3 times the power and twice the torque of stock.
Yes red loctite is needed.

dylan
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