Broken drive shaft

[blsfrs]

Originally Posted by FrickingReallySlow

Turning it 4 times to try to get rid of vibration is def PITA having to get new bolts each time. But also there were a couple of threads a while back about the bolts being too short with aftermarket shafts and results in only half your nuts thread engaging. Solution was to get longer bolts so that all threads engage. I still haven't done it yet on mine @blsfrs do you remember if all the threads engaged on yours?

I'll get some close up pictures of the break and mounting flanges of the 2 drive shafts.


Thanks for all of the input.


I did find out that there is a 1 year warranty on DDS aluminum shafts. My receipt is dated 12/20/2020. It broke on 01/14/2022. I've emailed Vivid racing and DDS but have not yet heard back.

[NoHaveMSG]

Originally Posted by FrickingReallySlow

Turning it 4 times to try to get rid of vibration is def PITA having to get new bolts each time. But also there were a couple of threads a while back about the bolts being too short with aftermarket shafts and results in only half your nuts thread engaging. Solution was to get longer bolts so that all threads engage. I still haven't done it yet on mine @blsfrs do you remember if all the threads engaged on yours?

On my DSS AL I had full thread engagement.

Originally Posted by EAGLE5

It's probably gonna be fine 999/1000 times in the first year.
But that 1/1000 is bad enough for a safety recall. 1/1000 * 100,000 cars is 100 failed cars that could kill people in the first year. And then the car companies look at a car's life over 20-30 years, and they start to sweat, because that 100 failures can become 10,000 or more if things go badly. Hence we get our valve springs recalled.

But you? In a car you probably inspect often? Fuggetaboutit.

Fair enough point.


@blsfrs I would call, not just email. If they don't help you out let me know. I have another spare stock drive shaft and a DSS AL that are both used. You can have either one for the cost of shipping. I only need to keep one as a spare and I have both these laying around.

[blsfrs]

Originally Posted by FrickingReallySlow

Turning it 4 times to try to get rid of vibration is def PITA having to get new bolts each time. But also there were a couple of threads a while back about the bolts being too short with aftermarket shafts and results in only half your nuts thread engaging. Solution was to get longer bolts so that all threads engage. I still haven't done it yet on mine @blsfrs do you remember if all the threads engaged on yours?

The DDS flange is quite a bit thicker. If I ever again use a non-stock drive shaft I'll use longer bolts. @NoHaveMSG: Thank you for your kind offer. PTuning sourced a shaft while they had it in the shop.

[blsfrs]

Originally Posted by Ultramaroon

Once the rear u-joint loosened enough for it to spin off axis, it was doomed. Still being fastened at both ends, it buckled like a bent straw. It looks like it may also have gotten scored rubbing against maybe the exhaust. Once a crack started, torque quickly finished the job.

Whole lotta guesswork based on those pics.

Pictures will probably lead to more guess work but here they are. Rubbing enough to cause scoring would make noise and I ain't that deaf yet. I would have thought that loose enough to deform would have been loose enough to cause perceptible vibration and my butt ain't that numb either.

[Grady]

Originally Posted by blsfrs

Pictures will probably lead to more guess work but here they are. Rubbing enough to cause scoring would make noise and I ain't that deaf yet. I would have thought that loose enough to deform would have been loose enough to cause perceptible vibration and my butt ain't that numb either.

Not enough definition in the pictures to tell. We will need to see grain structure in order to make a guess. What you are looking for is part of the separation being shiny and another part not, this is an indication of a fracture that was there prior to the failure.

Other thing you will be looking for is the rough fracture, Is the scoring folder over the fracture. An indication that the scoring happened after. Is the scoring not folder over, an indication the scoring happened prior to the fracture. This may be visible with a magnifying glass.

[Ultramaroon]

Originally Posted by blsfrs

Pictures will probably lead to more guess work but here they are. Rubbing enough to cause scoring would make noise and I ain't that deaf yet. I would have thought that loose enough to deform would have been loose enough to cause perceptible vibration and my butt ain't that numb either.

Even with the blurry pic, I clearly see a perfect circumferential cut which coincides with the failure point. Where your rear mounting screws really loose? Perhaps there was some intermittent contact with the exhaust leading up to the failure. Regardless, that's it. Doesn't take much to create a stress riser. It's like cutting glass. Sharp corners fracture easily.

[blsfrs]

Originally Posted by Ultramaroon

Even with the blurry pic, I clearly see a perfect circumferential cut which coincides with the failure point. Where your rear mounting screws really loose? Perhaps there was some intermittent contact with the exhaust leading up to the failure. Regardless, that's it. Doesn't take much to create a stress riser. It's like cutting glass. Sharp corners fracture easily.

IMHO, What appears as scoring is probably because the broken ends of the shaft were rotating on the deck of the dyno for several seconds after it let go.

[Opie]

Originally Posted by FrickingReallySlow

Subaru notes these as one time use items but I never understood why, if its not rusty/striped what's the mechanical reason they can't be reused?

Because bolts actually stretch when they are tightened to reach their torque value. Almost all driveline and suspension bolts are single use and should be used/torqued only once.

[CrowsFeast]

Originally Posted by blsfrs

IMHO, What appears as scoring is probably because the broken ends of the shaft were rotating on the deck of the dyno for several seconds after it let go.

If you flip the right side around and look at where the broken 'tab' fits into the left side, you can see a clear mark around the circumference that continues on both pieces. Definitely got scored prior to failure.

MS Paint skills below:

[blsfrs]

I guess the next step is to jack the car up and look for evidence of rubbing. The car is at stock ride height and has the oem midpipe. I don't recall running over anything that would have hit the driveshaft.

[bcj]

An unfortunate contact with a speed bump is as likely as damage from the undercarriage.

[Ultramaroon]

Originally Posted by bcj

An unfortunate contact with a speed bump is as likely as damage from the undercarriage.

That would leave a helical mark.

[dragoontwo]

Originally Posted by Ultramaroon

That would leave a helical mark.

And a dent in the exhaust.

[Ultramaroon]

Originally Posted by dragoontwo

And a dent in the exhaust.

Oh, yeah! Duh.

New *cough* twist: Exhaust briefly shoved into driveshaft while traversing speed bump. Package of fail arrives two weeks later.