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What Broke?


SSB

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Well, got a surprise today. Came out of a corner in second gear and bang, lost forward motion. Trans is working, drive shaft is turning and axles are ok. Thought I felt a vibration before the event. Speedo is reading and there's a bit of a noise near the diff. Anybody got pictures of what's connecting the drive shaft to the diff?

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Struggling to read French but 2801.63 appears to be the N9TE shaft. Would the splines inside the back end of the shaft broke away? I don't drag race it?

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I'd like to believe the issue is the drive shaft as the sound it makes with the clutch out is fairly light.  That said, I have another diff but not a drive shaft. The race car  (Red) never broke and has had a much harder life. 

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How did you determine if driveshaft is turning?  From your description it has to be drive shaft or diff - but it could also be clutch...

I'd suspect clutch over driveshaft or diff without more info...  Had the exact thing happen in a Scirroco - thought for sure it was transmission.  Resealed a replacement,  but on install the clutch disk was toast - center had broken out of it.  Replaced the close ratio with the regular 020 while I was at it along with the new clutch.

Rabin

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The noise it makes when in gear,  engine running is near or at the dif and the speedo is indicating is where my diagnosis lead me to drive shaft/diff.

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What kind of noise is it making?  Could be stripped splines, broken shaft, or something broken in diff. Hard to guess without more info on type of sound - but either way the diff has to come out to address any of the guesses.

Have never heard of this kind of failure, but does Deuce still have the open diff?  Good opportunity to upgrade to a lsd while you're at it.

Rabin

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Actually. Deuce has Red's original LSD (We bought a new diff for the 1989 season). I disabled the ABS and later replaced the ABS altogether. So that diff has 60K race miles on it plus the 70k while installed in Deuce.

Noise: It's a light sound, ticking with no vibrations in the car. Gear and engine speed related (faster in 5th and slower in 1st). For such as relatively easy life Deuce has had compared to Red, it's had a lot more failures. This is the first time it's stranded me, however.

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I would guess sheared drive shaft or some sort of sheared break in the diff...

Stripped splines would be much louder, same with ring and pinion issues.  Light ticking sound would have to be a fairly clean break.

Keep is posted on what the failure is when you find it.

Rabin

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Dang Victor - I've never seen that kind of break ever.

Too bad about going to an open diff - If you want to source an LSD I'm sure myself or Hugh can help out. :)  

I've always wondered what a 4.11 LSD out of an XN6 5sp sedan would do to perk up a Turbo.  

Rabin

 

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It was so gentle about it. No bang/crunch/snap/crackle or pop. Rolled in gear without any noise at all. I'm going to want a spare as Red's diff has about 140k on it but I never thought Deuce would be the one that needed it first.

diff 3.jpg

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Doesn't look like it twisted during failure (no spiralling) - Did mechanic mention if torque tube was loose or not?

Rare / odd failure so I'm curious what was the root cause was - or maybe it was a manufacturing flaw that fatigued over time until it was weak enough to break.

Rabin

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I felt it go off center (in retrospect ) but that was only a mile before it broke. Every thing was tight and in order except the oil had been leaking apparently for some time that I had not noticed.  There are two different surfaces there. One is maybe 15% of the surface that is rough and the rest is smooth. I'm guessing the 15% area is the originator of the final failure. Just guessing though. 

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The rough part is what was left and finally broke:

fatigue-failure-slides-7-638.jpg?cb=1384

 

The part (at least in this zone) can handle much more than 150hp, that's why the rough surface is only 15% in this case.

Threads are a common weak point, that's why airplanes have UNJF threads:

ThreadRootPic.GIF

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Good info. Using said info would suggest the upper and lower sections (11 o'clock and 5 o'clock) were the last to go. That said there is a little oxidation in the upper right quadrant. As so the fatigue is not an old one from when it was the race cars diff some 30 years ago. Surprising to me as I don't do burn-outs, jump berms, drift or any other hooliganism's with that car. 

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Although...  The car did do a bunch of jumps through the glass window over the bed - so maybe a tiny fracture started way back when? 

It's pretty well protected in that tube, and the splines looked OK from the picture you posted - so the only thing left are the jumps.  Maybe.

Rabin

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Well in the commercial, as I recall, the rear tires are not spinning much faster than the fronts. So the concussion of landing wouldn't shock the drivetrain anymore than my turn 7 Road Atlanta qualifying experiment where I left my foot down, left foot broke, turned off the key then turned it back on as I exited. Was a suggestion from a friend who was on Paul Newmans team. Well I'm here to tell you that was the single largest shock that drivetrain ever got. If it was going to break, it should have done it then but that is one reason I bought another diff for it anyway.

Reds_Commercial.avi

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I was thinking more along the lines of the jumps that caused your castor to be out of whack maybe tweaked the driveline at the same time somehow...

Now I have to ask just exactly was the reaction of the car when you turned the key back on?  I'm thinking unburned fuel - was it an 'explosive' exit?  :)

Rabin

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Axle Tramp and two clouds of tire smoke. Leaving the throttle open let the turbo stay at full speed so no fuel was being added as the ignition was off but let's just say there was no turbo lag when I turned it back on. All the way down the back straight I kept saying "Sorry Red"

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