[DeTomaso] stock halfshaft u joint

[Justin Greisberg]

thanks for those insights - so the u joint itself breaks?  So, in my case, where the press fit is not so tight anymore on one u-joint end cap, I should not expect a failure?  i can not understand how a weak press fit (not grossly loose) would make the half shaft fail, but I am curious what others have thought.
 

 



From: JDeRyke at aol.com
Date: Mon, 22 Apr 2013 02:55:14 -0400
Subject: Re: [DeTomaso] stock halfshaft u joint
To: justingreisberg at hotmail.com; detomaso at poca.com

In a message dated 4/21/13 5:57:47 PM, justingreisberg at hotmail.com writes:


what fails when the shafts fail?  What part actually breaks?


In the ones seen at PPC, the holes in the u-joint holders were reamed out oversize, probably from a prior u-joint failing, which first siezes, then begins moving in the normally press-fit holes. Being mild steel, it doesn't take long for the hardened steel cap to ream out the softer holder. Once that happens, the holder is junk.... and there are no individual replacement parts. A few had hairline cracks and may be weldable, but would need precision machining afterward to reestablish the normal press-fit.

In a few halfshafts used in cars with very high powered engines or that engaged in drag racing, the splines inside the halves actually twist, binding up the normally smooth sliding action. Again, the damage is irreparable and in most cases the halves have selectively worn together so replacing half the halfshaft assembly does not work. 

If a u-joint fails at speed, one end of the halfshaft breaks free & the splined halves extend. The 10-lb assembly spins wildly around striking whatever it can reach. If the inner u-joint fails (driven by the wheel),  the shaft will beat up the aluminum ZF case. Besides breaking the ZF cases (which can usually be TIG-welded if completely disassembled, the halfshaft usually bends. If the outer u-joint fails, one cannot get the clutch in quickly enough to keep the free end from vastly enlarging the hole thru the inner fender and ripping up rear brake lines and associated suspension parts. FWIW- J DeRyke