my own worst enemy-half shaft bolts

jvandyke

jvandyke

True Classic
Took X to work. Heading home. Street light, busy intersect, take off "clunk" no go. Push myself into lot thinking the clutch grenaded. driver's side half shaft let go (right term?) axle separated from output flange, bolts had loosened up I guess. One sheared off, the others survived. I'll replace them all of course but apparently I need to know the proper method here, loctite? Maybe hex heads with locking tab washers this time around? I've had them loosen up before but caught it, this time obviously not. Oh well, probably no lasting harm done beside my pride which my X has long ago brought into proper perspective. :eyepop:
 
Last edited:
Hmm...

The proper bolts and double-plate washers and correct torque (31 ft. lbs.) should result in bolts that stay put.

4393157.jpg

4315446-OE.jpg
 
jvandyke said:
apparently I need to know the proper method here, loctite? Maybe hex heads with locking tab washers this time around? I've had them loosen up before but caught it, this time obviously not.
Click to expand...
Definitely use loctite, not just for its locking ability but also because you'll get better readings on the torque wrench.... And check your torque wrench to see if it's telling you the truth. Something is systemically wrong here if you're finding these bolts working loose.
 
Last edited:
Half-shaft bolting

Yes, new bolts because of shearing stress and proper torque but most important is to have absolute clean surfaces when bolting together. Any oil or grease film between surfaces will result in micro sliding of components and the loosening of fasteners. You will never squeeze out the lube. Being a millwright for over 40 years I have seen lots of loose and broken fasteners because of this. Glenn
 
That's probably what I was fighting; not clean enough.
Now, there's nothing special about these bolts right? They're not TTY or anything silly?
New bolts, super clean, little medium loctite, proper torque. Check them at the next couple oil changes. :nod:
 
This is very odd. I've never replaced a bolt and never had one loosen. Someone once told me that the correct tension was a "double head shaker" - which means I'm over-tightening them if correct torque is 31flb! But its never failed for me!

On the car I recently restored, the bolts looked like they had only been removed once (low km car and the heads weren't munched) and there was evidence of yellow stuff on the end - just like the stuff that comes pre-loaded on caliper retaining bolts - loctite from the factory?

The other thing That I would be suspicious of is that replacement bolts usually have a shorter "shank" and longer thread than the originals. May pay to check that the bolts you are using do not have thread near the shear interface? I've always been reluctant to use aftermarket bolts for this reason.

THis photo from Midwest shows what I mean:
4393157.jpg


I just measured an original one I have here and the shank is 30mm (vs 15mm) and the thread is 17mm (vs 30mm). (can take a photo when my phone charges)

At one stage I considered buying bolts with the correct length shank and parting off the thread so the bolt is the correct length - but IIRC I needed 120mm bolts and they were hard to find in themselves - plus the machining cost of cutting down all those bolts didn't appeal either!
 
Franken said:
This is very odd. I've never replaced a bolt and never had one loosen.
Click to expand...

I remember the debate, some swear you should never reuse, others have often with success. I'm 90% sure it was the installer who failed (me) to properly clean the threads and holes and then torque correctly. I clearly remember doing it, and rechecking them but I still take full responsibility and won't say preach "replace" or "reuse", just "be aware" and check 'em once in a while.
 
It shouldn't matter if the bolts are new, used, clean or greasy. If the bolts are torqued to 30 or so lb/ft they should work just fine. technically if the threads have oil or grease on them you should reduce the torque but this setup is over-engineered enough for a street car that there is plenty of margin for error. Now a race car is different and I would always replace the bolts. I wouldn't bother with thread lock in any case.

Also, VW axle bolts will work and are readily available (p/n N 911 08 201). They may need a little bit ground off the ends. They use a triplesquare socket and are much less prone to stripping than the hex.

Keep in mind that VW uses this almost identical setup in cars weighing 1000 lbs more and they hold up to 300+ ft/lbs of torque without much problem.
 
I reuse them, and before I put them back in, I make sure everything is clean (especially the mating faces).

I reused them on my race car MANY times over.. probably a few too many times, but never did I have an issue - maybe they never had a chance to get loose because I tore my car apart enough times, not sure.. the car was lighter but I abused it (GT racing).

Same on my '82 - I just clean out any gunk out of the heads, and ditch the ones that are in rough shape.


I mean, wheel bolts are subjected to the same kind of stresses - why wouldn't you need to replace those every time you take off the wheel?? (I know, stupid question... but that just popped into my head).

I've never had a CV bolt come loose.
 
myronx19 said:
I
I mean, wheel bolts are subjected to the same kind of stresses - why wouldn't you need to replace those every time you take off the wheel?? (I know, stupid question... but that just popped into my head).
Click to expand...

Wheel bolts are way beefier, so are far less likely to have been been damaged by stress cycling from undertorquing. There's actually no reason not to reuse the CV bolts if you know that they were properly torqued from the beginning... but they're cheap enough that it's easier to replace them than to take the chance.
 
Same bolts (slightly different length) used by Volvo on 97-99 AWD fore-aft CV joint connections. I've also re-used them many times over (3 times on the X1/9) without issue. I don't use a torque wrench, either. I have a long offset handle angle key, and thats what use.
Only thing I do is clean all surfaces and the female threads thoroughly (on the X1/9). On the Volvo there's no point as the threaded holes are capped by a cover that is full of grease, so the bolt threads get greased as they go in, no matter what.

I DO inspect the bolts for signs of stretching - you can see when it happens, there will be a 'wobble' or thinning of the threaded section, usually close to the shank in my experience.
 
bolts

a long time ago when I worked at the second fiat dealership, young and stupid enough to think I could build a stump puller 1300 with a 5 speed, I asked our bolt vendor for air craft Allen bolts to replace the axle bolts in the car... he just smiled and told me that aircraft bolts have more tensile strength, (stretch) but no advantage to shear strength. in order to get shear strength, I had to drill to install a larger diameter bolt:shock:
needless to say, I have used and reused flange bolts with no backing out or snapping
mikemo
 
I reuse mine...

I've never snapped a CV bolt on a Fiat/Lancia that I can recall. I've snapped a few on my VW's, mostly in removal/attempted removal.

My post was meant to convey the need for the weird 2-bolt washer, and the proper torque. I guess it goes without saying to make sure the mating surfaces are clean.

I always use a torque wrench on things like this, and go around twice once my torque wrench starts clicking, just like I do with wheel bolts/nuts. On CV joints it can be a PITA but I can't recall having one come loose. I have found one LEFT loose hence my double checking by going around twice with the torque wrench.
 
Is there supposed to be a wad of grease packed between the shafts? What is the purpose of the two bolt washers? If they had locking tabs to fold up and hold hex head bolts I'd feel better about the whole thing.
 
Mr. Franken, I found some at my local Lowe's home...

improvement store... in various lengths... but this was a drawer that had not been opened or re-stocked in a long time. I also found an old Mom & Pop-type hardware store that stocked all sorts as well, including 10 and 12 x 1.25mm bolts and nuts used in many places on our cars.

My local auto parts stores didn't have these!
 
Yeah Jeff... I had a similar incident... I lost...

one bolt and then the other loosened and the "two-bolt washer" was swinging and hitting the chassis making one hell of a racket.

I looked under the car and tightened the remaining bolt with pliers but it did it again at about 50 mph... so I just slowed down and nursed it home for the remaining 15 miles!

I truly believe your bolt sheared AFTER the coupling loosened... because as so many others stated... if the surfaces are clean and the bolts tightened evenly (to specs) there should not be a problem.

I purchased some bolts at Lowe's and used some Loctite on them and have pulled and reinstalled my trans at least four times, and have NEVER had a problem. I don't believe at 31 pounds there is a "torque-to-yield" issue as if we were installing head bolts with a gasket in between.

Do pull all your bolts, clean them up as well as the mating surfaces, use Loctite and like you said... inspect them again at your next oil change. You should be fine.

Oh... and the Loctite will protect threads from rusting somewhat too!
 
You must log in or register to reply here.
Back
Top