I have been repairing Corvettes for a very long time and I know I have not seen it all..and this just proves it again.

I have seen broken U-joints and the eyelets in the half shafts wear and break...but NOT this. This is a new one.













I am sorry if these photos are not crystal clear. I never claim to be a professional photographer. BUT..I can say that the tube literally appears to have peeled off and it peeled right back from the weld.....so the end of the surface of the tube is smooth.

The owner who sent me the car for repairs told me that he as pulling out onto the road and driving normally ( no crazy stuff) and when at about 45 MPH and it changing into possibly third gear....due to being an automatic...the half shaft did what you can see.

This is a 2-1/2" diameter half shaft on a 1969 Corvette.

Not that I do not inspect parts very well...but I now know I have to look at his area when I am working on replacing U-joints or whatever. I know this seems to be a rare case ( at least for me because this is the FIRST ONE)...BUT...for me...all I have to see it happen one time and then that adds another visual inspection I feel I need to do to make sure parts are correct.

DUB

 

Thanks for the post. The amount of rust suggests that it was de-laminating for awhile, possibly. That it happened on an automatic car is shocking......I too have never seen this in 40-odd years of servicing cars and trucks. A new one for the books, to be sure!

 

Actually the rust is SUPER LIGHT surface rust due to is was raining today. I can not see any serious cancerous rust that was showing any pitting where the rust has been there for long time.

This is very strange.

DUB

 

U-joints look plenty strong............

Larry

EDIT: Dub.......is the half shaft an original GM piece, or could it be a piece that was "made to fit" by a driveline shop??

 

original.

Dub

 

One of my original half shafts was twisted when I rebuilt my car. The u-joints on both ends were no longer clocked together. But at least it was holding together. That thing has all sorts of suspicious issues - the tube seam split cleanly open. The yoke end doesn't seem to show much evidence of weld penetration. I'm pretty amazed it happened on an automatic car also.

 

 

Could be a defective shaft from the get GO

 

Kinda looks like the weld failed then twisted apart. Seen some failed half shafts before, never one like that.

 

Like such:??

 

I like that one!

Those are drag slicks on the car, right. Corvette IRS and drag racing don't mix.

 

If built correctly with the right parts they do.

 

Nope, disagree. Eventually an IRS will fail in this situation. Too many week points in the system.

Drag racing, even with a Corvette, means solid axle.

Yes, I know many of you have drag raced successfully with IRS systems without a failure ... yet! But it will happen IF you are putting any serious horsepower to the ground.

 

These things are 50+ years old. Metal fatigue always lurks. Be ready for anything.

 

Yeah - I'm thinking a defect or the piece was just past its time....
I feel that way some mornings...

 

This is the axel on a midyear corvette Think abbot that when you take off really hard.

 

Basic mechanical design rule: The joint should be stronger than the surrounding material.

This is evident in the twisted halfshaft, and the mild steel tubing is very ductile, so it deformed significantly, but didn't break. IMO the design is good, but was stressed well beyond the design limit, likely due to a big displacement engine and 5000 RPM clutch drops with sticky tires.

Back in the seventies McClellan and company instrumented the drivetrain on a test Corvette and subjected it to shock loads. Prior to the test the engineers bet on the maximum loads they would see, and the test results showed loads THREE TIMES the highest estimate. (The test is discussed in his book.)

The weld failure could have been a manufacturing defect in either the tube weld or the weld that attaches the yoke to the tube, and fifty years of fatigue finally propagated a crack long enough for failure to occur. Localized corrosion can also create a surface defect that can propagate as a crack with cyclic loading, eventually leading to failure.

Finally we don't know what kind of abuse this car has seen, but as was previously stated, you never know what can happen to a fifty year-old car, so frequent inspections are necessary, just like an old airplane.

It's a good idea to Maganflux critically loaded engine and chassis components during major rebuilds or restorations - crankshaft, conn. rods, spindles, differential case, etc. so maybe halfshafts and the driveshaft should be added to the list.

It looks to me like the failure started where the tube seam meets the yoke and a Magnaflux inspection would have very likely revealed a significant defect.

Duke

 

Wow !! ....I think the Beatles said it best ........

 

How much extra does all this pickin', pokin, checkin', magnafluxin', Xrayin', cost the customer when you come if for a check up?

Probably should replace the u-joints while your at it. A broken U joint would cause the same problems. Just hope you don't get a bad joint out of the box.

I know some will fall for it. You can't be too careful just how much?

 

I do a very good basic visual inspection when I work on them....but no X-rays or magnafluxing.

More than you might think. Becasue I am not driving through town for nothing...and then having to wait for it to be checked...and go back and get it (if I had to leave it). By the time the 'smoke' clears....it would be a serious bill.

I will keep this part and show people...and let them decide what they want to do on their own car that is driven on the street.

And keep in mind this guy was not out there beating up his Corvette....and that does not mean much due to we do not know how it was driven by previous owners.

DUB