New CV bolts turning out after just several days

[Sodo]

Agreed.

If the bolts were Allen-heads, I might have (in a former life) tightened them with an L-Wrench.
So they would have about 16 ft-lbs.
And it’s physically impossible to pull 80 lbs at 5” to get 33 ft-lbs on an L-wrench.
Lots of L-wrenches would be used and nobody would pull that hard.

Then you’d have a situation where everyone’s trying all kinda bolt retention methods, from q-tips to aircraft hardware.

All hail the triple-square!!!
And the 20-30 years of tested success for the 33ft-lbs.
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[?Waldo?]

I have no issue with getting a decent swing on my clicker torque wrenches when installing CVs. I also use the torque wrench for all fasteners where a torque spec is specified. I have been wrenching long enough that I have an excellent hand feel for torque but using a torque wrench reduces my own stress when hurtling along at 70 MPH in a 30 year old metal box.

[?Waldo?]

In looking up typical torque values, for an m8 10.9 bolt that is lubed the typical torque value is 24 ft-lbs. 33 ft-lbs is a 37.5% increase over normal 10.9 torque and considering that all of the other M8 fasteners on a vanagon get the 15-18 ft-lb specs, it is 83-120% higher than what is typical for M8 fasteners on a Vanagon.

[0cean]

[djkeev]

[?Waldo?]

[Merian]

[AZ Landshaper]

anyone who has had a cv come loose a better than 45mph will be damn sure to do the job correctly the next time. That is some loud and aggressive pounding and will scare the be-jesus out of you. BTDT
_________________
Support Small Business.

-------------------------------------------------------
85 Weekender w/ EJ22
Previously
64, 71, 72, 73, 76, 81, 84, 85 & 87 Campmobiles and Westfalias
and a 67 bug.

[levi]

[0cean]

[?Waldo?]

[Sodo]

A “very experienced” local VW shop R&R’d my trans once and the CV bolts were all loose after a few days. I thought they “forgot” to tighten them. I tightened them “by hand” to the 26 ft-lbs number. Then checked later and they were loosening. So I tightened again. By “calibrated hand-torque wrench”. I had 26 ft-lbs in memory, didn’t look at spec in the Bentley.

Some years later (2015?) I “learned” of the 33ft-lbs spec, and was astounded how “friggin tight” that was.
For a the last few years I thought 33 was a “rogue-mechanic” Vanagon hack.
I wasn’t buying into the dry-threads thing ‘cuz I have the ability to go under the van and check up on the bolts. And I know that a greased bolt “ends up tighter and has less “wind-up torsion” that acts to unscrew a dry bolt. And that when the grease oozes out of the highest pressure thread contacts, it starts to lock in place. And I could go under the van and re-check. Which I did, and they were staying tight.

But I still do “33 and a later re-check” because I can, its extra, but easy. Just like Ocean does the loctite, because he can and doesn’t mind the little extra work “to be sure” on his 30+ year old van. There’s lots of things we do “to be sure”.

We recommend everyone to change their fuel hoses. I sure hope the OP takes the van to an experienced mechanic to check up on his fuel hoses...

[?Waldo?]

It's hard to know. I was assuming that at least he set the specified 33 number regardless of units.

Someone using the NM scale and setting to 33 will also undershoot the correct torque and instead only torque to 24 ft-lbs which has been shown to be problematic.

[0cean]

[quote="?Waldo?"]

[crazyvwvanman]

You must have been doing something wrong. I've changed countless CVs, CV boots, axles, etc in my 40 years of CV axle VW van work and never put Locktite on CV bolts. Always use the later 12 point CV bolts, with stock plates and washers.

Mark

[Abscate]

AN undamaged grade 10.9 M8 fastener torqued correctly to 33 ft lbs won't loosen up under use in a CV application. If yours do, something isn't right.

The number of ways the tech can screw it up are infinite, but the fastener and torque are not to blame
_________________
.ssS!

[0cean]

[Sodo]

New, ambitious Vanagon-mechanic-to-be has a go-for it attitude, charges ahead,
but does not have an experienced mechanic nearby to ask about "the details".

New Vanagon mechanic tightened CV bolts to 33 inch-lbs (2.75 ft-lbs) and they came loose.
Two times.
A similar problem (torqued bolts loosening) happened with the Flywheel bolts in April in another thread:
Flywheel Mount After Wrong Bolts Jammed Into Crank

[Abscate]

Paul Simon - Fifty Newton Meter Ways to Fubar a CV joint bolt on..

Im sure there are more

Lousy torque wrench from Garbage Freight
Poor socket - torque lost deforming head rather than tightening fastener
Fastener Quality- Novices think "parts from VW Heaven" are good. Mechanics inspect parts regardless of source. Supply chains change. Daily.
Poor torque use. Novice with torque wrench and extender bar will not apply set torque to fastener.
Damage to CV face
Damage to threads in flange
Damage to fastener
Cross threading
Not adapting torque to lubrication
Wrong Bolts - depth too little or too much
Galling on head friction surface
Crap in threads
Warped/bent flange
Bent axle
Preload on rear wheel bearing
Excessive filtering of transmission gear oil (ok, I made that up for you, Sodo)
_________________
.ssS!

[?Waldo?]