Forward several days and at least another 100 miles and I had taken the Pantera to a local muffler shop to see if I could possible get a little more space between my exhaust system and the left rear tire. We got the car up on the lift and found out that there wasn't any real issue with the exhaust but while we were looking around we noticed a large crack in my Spicer half-shaft at the outboard flange. A weld had completely broken all the way around the shaft. The source of that mystery "BANG" a few days prior had suddenly been located!
What completely amazed me is that the half-shaft did not come apart. The resulting carnage of what happens when a U-joint fails on a Pantera half-shaft as one end of the shaft tries to beat the entire inner structure of the Pantera into submission is NOT pretty.
Upon closer inspection, you could see that the two parts of the outer flange and "spun" and made the two ends of the half-shaft out of phase by about 30 degrees. I was surprised I didn't have a bad vibration because of it. What caused the two parts to "catch" after they spun was a section of the broken weld wedged it.
I called my engine builder, Gary McGlasson, (McGlasson Racing Engines) to tell him that I thought his dyno was off by about 200 horsepower. He asked me why I thought so and I told him because my Spicer half shafts were rated for 700 horsepower and he had dynoed my car at 540 HP. I figured that I must have had 699 HP at the rear wheels because if I had just one more horsepower, I would have split the half-shaft in two!
It was a fun thought anyway....the 699 HP at the rear wheels, not the catastrophic failure
I took the half-shaft to Gary and he inspected it and said that the original weld had not been done correctly. The weld had flowed to one side of the shaft and not bonded to the other. The break was very clean on one side. We drove down the street to a local U-joint shop that a friend of Gary's owns and they ended up having the Spicer flange sitting on the shelf! I couldn't believe it! When the owner of the shop saw the cracked flange he told us that in all the years he had been in business he had never seen a failure like that. I told him that Gary built the engine for the car that broke it and he said "No wonder it snapped it like a twig!"
Too much power is a lot of fun but it can be hard on the equipment
I checked my receipts and I had installed the Spicer half-shafts back in 1993 when my Pantera had 54,000 miles on it. The odometer just recently turned 140,000 miles so I got almost 90,000 miles out of them before this incident. By the way, the U-joints had never been replaced and looked great (lubing them at each oil change pays off!)
Here is a shot of the new Spicer flange:
