How could that happen? Bad driveshaft!

[SamS14]

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..

 

[SamS14]

Second pics

 

[SamS14]

Last one!

 

[CoryPad]

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?

 

[SamS14]

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.

 

[SamS14]

thread view

 

[thruthefence]

"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.

 

[SamS14]

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!

 

[SamS14]

And.. Thank you for the help you provide to us!

 

[SamS14]

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

 

[SamS14]

Where the pen ball are, is there the hub finish, where the washer seat on the hub.

 

[mfgenggear]

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.

 

[Tmoose]

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.

 

[mfgenggear]

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

 

[CoryPad]

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.

 

[mfgenggear]

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

 

[SamS14]

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!

 

[SamS14]

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

 

[YvesLLewelyn]

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?

 

[CoryPad]

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.