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Loose bolts in driveshaft coupling.
06-03-2017, 05:00 PM
Post: #1
Loose bolts in driveshaft coupling.
For the third time now all the bolts in the left (rear) outer driveshaft coupling have come undone despite having fitted anti-vibration washers and Loctite last time it happened. It's always the left rear coupling. My theory is that it's caused by vibration due to driving a lot on corrugations because the inner joints (CVs) don't receive any up/down movement so would have less tendency to slacken, and the right side bolts turn in the opposite direction so would tend to tighten instead.

Last time this happened, in August 2015, I removed the left driveshaft on Dean's advice, engaged the difflock and drove 300km home in "one-wheel-drive". Fun!

It's quite interesting but I need to find a fix for this now. Does anybody know of one?

Thanks
Colin
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06-04-2017, 11:00 AM
Post: #2
RE: Loose bolts in driveshaft coupling.
put your bolts in with copper slip grease, also tighten them 3 times in a circular motion, also try get spline bolts, rather than allen bolts, they can tighten with more force

I may be a mechanic, but i can't fix stupid
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06-04-2017, 04:11 PM
Post: #3
RE: Loose bolts in driveshaft coupling.
Thank you Stuart, I have the 12-point spline bolts already, they came with a new set of couplings last time this happened. Are you recommending copperslip on the threads or under the heads of the bolts? The threads were loctited last time and that didn't help even with the anti-vibration Heico-Lock washers. {For type see the image (http://www.heico-lock.co.uk/Images/homep...age.gif)}.

I haven't stripped the hub personally, it's been done by a good workshop who are quite embarrassed that they can't find a solution to this and didn't charge me this time, so I haven't seen the internals personally but I was wondering if there might be room for longer bolts with nylock nuts on the outside of the axle shaft coupling. What do you think?

Thanks
Colin
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06-04-2017, 08:24 PM
Post: #4
RE: Loose bolts in driveshaft coupling.
I have also read that these bolts need to be torqued up to 35 Nm. Did you use a torque wrench to fit them?

1989 2.0i Syncro Camper (in progress!)
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06-05-2017, 05:27 PM
Post: #5
RE: Loose bolts in driveshaft coupling.
I didn't do it but I gave them the torque value and asked for 1/8th of a turn more.
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06-27-2017, 09:13 PM (This post was last modified: 06-27-2017 09:15 PM by Adrian.)
Post: #6
RE: Loose bolts in driveshaft coupling.
I had a similar problem some time ago which followed the replacement of all bolts on the rear CVs. The root cause was related to the bolt type i.e. the new bolts' shank diameters were less than the thread diameter.

It seems this resulted in movement between the CV and the hub due to torque. This in turn caused the bolts to work themselves loose.

Since replacement with bolts where the shank and thread diameters were the same I've had no issues; more than a year now.


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06-28-2017, 12:20 PM
Post: #7
RE: Loose bolts in driveshaft coupling.
(06-27-2017 09:13 PM)Adrian Wrote:  I had a similar problem some time ago which followed the replacement of all bolts on the rear CVs. The root cause was related to the bolt type i.e. the new bolts' shank diameters were less than the thread diameter.

It seems this resulted in movement between the CV and the hub due to torque. This in turn caused the bolts to work themselves loose.

Since replacement with bolts where the shank and thread diameters were the same I've had no issues; more than a year now.

This is the best theory that I have seen to date for the cause.
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08-26-2017, 04:04 AM (This post was last modified: 08-26-2017 04:06 AM by unclekenz.)
Post: #8
RE: Loose bolts in driveshaft coupling.
Idea Do it once, do it properly. Replicate what was done in original factory build.
Use ONLY the original genuine OEM undamaged/unworn and spotlessly cleaned fastening components.
Take the time. Be patient. Be thorough. Meticulously degrease/derust/clean/dry all mating surfaces and components till they shine.
Absolutely DO NOT USE any lubricant or locktite.
Re-install parts and evenly tighten all in STAGES in crossover pattern, similar method to evenly torqueing a road wheel, achieve even and correct final torque to all bolts.
Doing anything else is just plain wrong, leading to failure as described. Blush
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