greasable u joint failure pics
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
No explanation.....but I've put a file to the bearing surface of each and the HD non-greasable seemed to be harder.Its been awhile but I think the cap is a closer fit also.
Thread Starter
Racer
Joined: Mar 2006
Posts: 264
Likes: 1
From: west central INDIANA
New pixs. The Hole thru the trunnin is stepped, large hole is .312, small is .250. O.D. of trunin is .653. The color inside the holes are of a gold tint like heat treating usally looks.The joint was in fact put in backwards, zerk facing wrong way. I find no sign of rust, and the bent bolt was from the result of the failure. The end caps had not rotated, the joints showed normal wear, but not worn out. I have owned it 3 years mostly working on the cars front end and motor. 1700 miles total, buy me. never in rain.
Melting Slicks
Joined: Jul 2005
Posts: 2,545
Likes: 3
From: 406ci SB, AFR 180 Heads - 490 HP @5,600 RPM 529 lb-ft @ 4,100 RPM
I'd bet the retainer clip came out at some point and the u-joint slowly moved to one side and fell out. The damage you are looking at most likely was caused by hitting the road while spinning until you stopped. By the damage to the driveshaft the u-joint ends broke off after bouncing & banging around the bottom of the car and road.
My 0.2
My 0.2
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I'd bet the retainer clip came out at some point and the u-joint slowly moved to one side and fell out. The damage you are looking at most likely was caused by hitting the road while spinning until you stopped. By the damage to the driveshaft the u-joint ends broke off after bouncing & banging around the bottom of the car and road.
My 0.2
My 0.2
That's happened to me before in a truck. Half of the U-joint slipped out sending it way out of balance. The other side stayed in, so it just vibrated like a death machine until I came to a stop to see what was wrong.
I limped it home at 10 MPH...anything higher and it would start vibrating. Once home I got the drive shaft out and replaced the U-joint. Back on the road within 15 minutes.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Well, "permanently" lubricated U-joints are intended for the normal life of a vehicle....not for almost 40 years. Grease dries out after 5-10 years; then the joint is working "dry". You have to replace them when they no longer perform their function. For real permanence, the kind with Zerk fittings allow you to continually keep the grease 'fresh'. If they aren't overloaded, those really should last a lifetime (or more).
From the photos, it appears to me that the joint fractures may have started at the machined undercut near the base of the trunions. That machined undercut can create a stress riser at a highly stressed area in the joint and cracking can initiate there. Once one side started to 'work' and gain movement, the entire load moves to the other side and it cracked as well. About any loading at that point will cause both trunions to break off and the joint is gone. Just replace them with Moog or other well manufactured joints (not stuff like Dura-junk from Auto Zone!) and you shouldn't have another problem like that one. If you go WOT occasionally, get the greasless joints; if you don't, get the Zerk kind if you want.
From the photos, it appears to me that the joint fractures may have started at the machined undercut near the base of the trunions. That machined undercut can create a stress riser at a highly stressed area in the joint and cracking can initiate there. Once one side started to 'work' and gain movement, the entire load moves to the other side and it cracked as well. About any loading at that point will cause both trunions to break off and the joint is gone. Just replace them with Moog or other well manufactured joints (not stuff like Dura-junk from Auto Zone!) and you shouldn't have another problem like that one. If you go WOT occasionally, get the greasless joints; if you don't, get the Zerk kind if you want.
Tech Contributor
Joined: Aug 1999
Posts: 15,156
Likes: 3,965
From: Connecticut, USA
I cracked in half USA made zerk joints with a 250 hp vette with 336 gears- no loading. I have since used nothing but Spicer solid joints in my cars and the shafts I rebuild. Building some 3.5 shafts now with the same joints. Those appear to be more of a mfg defect then the typical cracking. If you look up my threads on U-joints you'll see the one I broke as well as the ones I haven't. Even when the posi cracked in 1/2 from abuse on one of our cars the Spicers were rock solid and re-used without a problem. I've run spicer that had the cap popout and those didn't break either. they cost about $10 more then the junk in the chain stores but they're worth it.
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Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
However, it doesn't put any more stress on the joint or relate to this failure...other than the joint wasn't greased for 3 years [because you couldn't get a grease gun on it].
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Instructor
Joined: Dec 2004
Posts: 196
Likes: 0
From: holland pa
another reason to invest in half shaft safety loops these are used for racing applications true, but the design of the vette IRS almost warrants them to be installed (just in case) i think there is a company called "drag vette" that sells them pretty reasonably and the small amount of investment involved there, would give peace of mind and definitely "control" the damage field. even a stock 190 h.p. is still capable of producing some significant torque and torque is what caused this not horse power.
........................................ ..........chris
........................................ ..........chris
Last edited by ve77er; Nov 7, 2008 at 11:22 AM.
Instructor
Joined: Dec 2004
Posts: 196
Likes: 0
From: holland pa
thanks for the photo binnie77!! i found the phone number for drag vette products it is 1-877-422-0943 and the pair of half shaft safety loops sell for $119.00 compare that to what you'd spend for rear repairs if the half shaft lets go!!
..........................chris
