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How could that happen? Bad driveshaft!

How could that happen? Bad driveshaft!

(OP)
How could that happen? This is the question that wake me off this night. and i have absolutely no answer for this...

Now i'm a mechanics, in a 3 door garage, one costumer came ( a beatyfull swift 2006... ) with 2 wheel bearing that make noise.. Ok, i'll change them when the ordered bearings are coming. So, to next week!

Friday, the bearings coming, we call the costumer, then he came to change them. I change them, drive test, no problem, even take me 1 hour less than the previously estimated time!

So... Drinnnng, Drinnng, monday! Costumer call back, and explain me that saturday he want to take his car and a big piece get through of his plastic wheel cap during the night... Ehh, ''Wait, i'll get on tow to take your car!'' I'm thinking in my travel to take his car with my towing, wtf, mabye he's wrong!

So i go at home of my costumer and found the draveshaft nut with a drive shaft piece on the ground, near the sidewalk to the house, with some pieces of plastic wheel cap.. Yayyy, now WHATS WRONG? Nothing into my repair was disturbing me, i know what i've done, I even put some spline lubrican on spline of cvjoint, torque it to 221 lb/ft, ( according to mitchell ), use a bearing press to put the hub into the bearing.

See the pics, I really don't understand what happen, and I really need a explanation for the costumer..

 

RE: How could that happen? Bad driveshaft!

A fracture in the splined region suggests only partial spline engagement.  Your installation method (using a press plus lubricant) seems like it should produce full engagement, not partial engagement.  Thus, it is possible that the assembly torque was not sufficient to fully seat nut, which may have allowed the spline to disengage.  Did you clean the threads on the shaft and the nut?  Did you use any lubricant on those?

RE: How could that happen? Bad driveshaft!

(OP)
No, i don't clean the threads and the nut threads, but when i took the driveshaft off the hub unit, they was clean, and i put some spline lubrican on them. I use the press to put the hub into the bearing, then put the driveshaft into the hub. The splines and the nut are not used in this case to press the hub into the bearing, and the only hit that a made to him was the lock of the nut. The driveshaft was completely free into the bearing.

I do not think the splines could not get into the bottom of the hub. When i took the nut with the parts of the driveshaft from the floor, the nut wasn't jammed, it was free for like 1/16 turn, because of my lock.

And when i torque it, the old lock mark on the nut was a the same place that the new lock mark, so i dont think that cvjoint wasn't at the place that should be.

RE: How could that happen? Bad driveshaft!

"No, i don't clean the threads and the nut threads, but when i took the driveshaft off the hub unit, they was clean, and i put some spline lubrican on them"

Is the Nut supposed to be "lube torqued"? Because that is what you did.

RE: How could that happen? Bad driveshaft!

(OP)
No, on mitchell installation procedure it don't talk to add spline lubrican on threads but i don't put too much. This could really do this?

I repeat that shaft ''explode'' on night.. and nothing get suspect, or i don't do something that i'm not sure when i was install it. This is so wierd!

RE: How could that happen? Bad driveshaft!

(OP)
And.. Thank you for the help you provide to us! :)

RE: How could that happen? Bad driveshaft!

(OP)
As you can see on the thread view pics, there is no many thread lubrican

RE: How could that happen? Bad driveshaft!

Sams14

by putting lube on the threads it now torquing more than 221 ft lbs. & spline shaft may of had a week or a defect.
thus it cracked while torquing the nut.

What was used for Torquing? Torque wrench or air impact wrench.

MfgEngGear.

RE: How could that happen? Bad driveshaft!

I would have expected the threads, the nut, or the necked down area between the thread and start of the spline to fail from over torque.

RE: How could that happen? Bad driveshaft!

Interesting issue
I was talking with one of the old timer here at my job, who has cold heading experience. it appears from the picture there was a seam where the spline shaft failed.
by looking at the picture, the center had tearing where as the outer portion of the spline had no tearing but a clean break. so "this is one theory". at the area of failure. it was smaller than the threaded area due to the seam where it had failed.

MfgEnggear

RE: How could that happen? Bad driveshaft!

None of the provided pictures have sufficient resolution to identify a seam.

The reason for the different fracture surface appearance is due to the heat treatment - the outer portion was induction hardened while the center is in the as-rolled/forged condition.  The induction hardened region has high strength, low elongation while the center is the opposite.  This leads to the flat and rough segments on the fracture surface.

Based on the information provided, partial spline engagement looks like the reason for the fracture.

RE: How could that happen? Bad driveshaft!

Corypad

That where my thoughts originally too.

but what was explained about the cold heading also made sense.

but it would be unusual to have partial engagement of the spline, because the nature of the assembly.
I have done a few of those replacement of the high velocity shafts. it's not fun. generally it's full proof when re-assembling. it would be most unlikely it was only partial spline engagement. however any thing is possible.

Cheers

MfgEngGear

RE: How could that happen? Bad driveshaft!

(OP)
First time, i use a air impact wrench, stop it right to the old factory lock mark...

But, if i was over-torque it because the thread lube, why cvjoint did not broke when i torque it? Or why the thread did not break when i torque it?

It break when the car was stopped for a long period! Not in my bay!

RE: How could that happen? Bad driveshaft!

(OP)
How could i done a partial engagement? I'm sure that cvjoint was fully seated!

RE: How could that happen? Bad driveshaft!

In the first photo supplied by Sam the end of the CV joint looks very rusty and pitted for a 2006 model - and there is rust on the face of the fracture as if it was all ready cracked somewhat.  Maybe the car had been in an accident that Sam didn't know about or second hand damaged parts from a wrecker had been used previously?    

RE: How could that happen? Bad driveshaft!

Sam,

I think you are correct to wonder why the threaded region did not break if you over-torqued this joint.  I think you did not over-torque this joint.

Perhaps the joint was fully seated, but perhaps the preload was not high enough to resist loosening.  If the joint loosened, then the spline could disengage during vehicle usage.

I think Yves comment regarding corrosion is not correct - a vehicle that is at least 3 years old in Quebec will have corroded constant velocity joint shafts if they are uncoated.  The rust on the fracture surface appears to be light, likely it formed in a short amount of time (days, not years).  The mating fracture surface has no corrosion visible on it.

RE: How could that happen? Bad driveshaft!

Cory

look at sams first picture there is a rust stain

Mfgenggear

RE: How could that happen? Bad driveshaft!

Yes, and look at his second and third pictures of the mating half - there is no rust.

RE: How could that happen? Bad driveshaft!

"The reason for the different fracture surface appearance is due to the heat treatment - the outer portion was induction hardened while the center is in the as-rolled/forged condition."

While I agree with the reasoning, isn't that a deep heat treatment layer? Usually that drastic of a change in Beach marks indicates that the outer diameter failed due to fatigue, while the inner area failed very quickly.

"by putting lube on the threads it now torquing more than 221 ft lbs. & spline shaft may of had a week or a defect.
thus it cracked while torquing the nut."
Agree. An impact wrench is not a calibrated torque device, unless it is calibrated, and I doubt yours is. My guess is that the marks lined up because you turned it 360° too far.

ISZ  

RE: How could that happen? Bad driveshaft!

The photographs did not show any beach marks.  If the part were through hardened uniformly and shows two fracture surface patterns like this one, a possible scenario is fatigue or environment assisted cracking followed by ductile overstress.  

In this case, it is possible that fatigue or EAC continued from the hardened case into the softer core.  But it wouldn't surprise me if the case were that deep - the core properties are so low, that a deep case is helpful for static and fatigue strengths.

RE: How could that happen? Bad driveshaft!

Looking at a Fractography Of Shaft Failures chart and given the shape of the fracture zone and its position; would I be correct in saying that this shaft failure is as a result of high nominal stress, sharp notch, rotating bending?

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181
 

RE: How could that happen? Bad driveshaft!

I think there are a couple of things that nobody seems to have commented on.
 Firstly - the car originally had wheel bearing trouble - unusual for a reasonably new car. Accident damage?
 Secondly - is that a big fractured chip out of the end of the drive shaft?  The shaft would presumably be totally unstressed in this area. Only a mighty whack from an accident could do this.      

RE: How could that happen? Bad driveshaft!

(OP)
CoryPad, When you say, disengage, do you think that cvjoint loose enough to slide out off my hub until the place that were broken?




Sorry for my absence, I was on vacation, so thank you all for helpfull answers!

RE: How could that happen? Bad driveshaft!

(OP)
YvesLLewelyn, I don't think that car was accidented, those bearings where diagnosticed by me during a road test for the rear brakes noise.

The car has just 63000km, I think those front bearings was just cheaper that other brands...

But, look at the IMG_3558, there is a little rust, or ''mabye'' some dirt, but that are at the same contact place of the IMG_3560, according to the notch on both fractures.

RE: How could that happen? Bad driveshaft!

(OP)
The big notch on end of threads are done at factory, This is the locking point for the nut.

With a cold chiesel, hit softly the non-hex side of the nut, just to fold the nut to prevent self-loosening

RE: How could that happen? Bad driveshaft!

Sam - I did wonder if that was a notch for locking - but in picture IMG 3561 it looks very battered.

  63000km (about 40,000 miles) - this is almost a new car by my standards - even less likely to have wheel bearing (or any other) problems.
 What make of car is it?  

RE: How could that happen? Bad driveshaft!

Sam,

Yes, I was suggesting it could be possible that the CVJ slid out of the hub.

RE: How could that happen? Bad driveshaft!

Naturally this part needs a full met. exam to find out, but that appears to be a hydrogen-related fracture to me.  No visible beach marks and no corrosion/discoloration on the fracture faces rules out fatigue, IMO.

A hard steel part, constant high load, corrosion all over the outside from rainwater (+ salt, probably), H has got to be involved in a big way.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein  

RE: How could that happen? Bad driveshaft!

True story.

Back in the 70s, a major auto manufacture was doing durability testing on a closed track.  After about 10k miles the alternator bracket broke.  It was replaced but failed again after another 10-15k.  When the third one broke, the car was pulled off the test schedule until "root cause" was identified.

The driveshaft (RWD vehicle) was so out of balance that it was moving the tail end of the transmission back and forth about 1".  The way the engine transmission mounts are located in that kind of a vehicle, it caused the front side of the engine [/i](where the alternator was located)[/i]to move forward and back a couple of inches !  Alternator brackets were never designed to take that kind of load !!

RE: How could that happen? Bad driveshaft!

I bet the test driver's ass was numb before this exercise was over.

RE: How could that happen? Bad driveshaft!

Yeah, I'm surprised they were scratching their heads over an alternator bracket failure, when I sure the vehicle was shedding parts all over the test track.

RE: How could that happen? Bad driveshaft!

Very interesting failure.This is a pure tensile break, which I have never seen in a CV joint stem before.It was a one time failure, as there is no deterioration to the fracture. The depth of the induction hardened zone relative to the stem O.D. is fairly typical. No evidence of fatigue, pre-existing cracks, chevron bursts from heading,hydrogen embrittlement or SCC. The only question is where the heck did the load come from?

RE: How could that happen? Bad driveshaft!

A driveshaft inbalance causing 800lbs, give or take, of engine and transmission to vibrate about 1" side to side and 2" front to back? And even if that was occuring, the driver could not tell something was seriously wrong? And we should believe this story?

Besides, what was causing the load on the alternator bracket? The resonant frequency of the engine and transmission moving like that would not be high enough to really have much effect on the alternator or it's properly designed mounting brackets. So, was it hitting something? And why wasn't the impact damage noticed?
 

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