I have repaired Jeeps that were eating U-joint in around 1-3000 miles. I found bad rear yokes. They let the cups wobble around. these were strap not ubolt. Ron
Also, I have seen a few folks gorilla over-torquing the fasteners, even to the point of breaking them, and wondering why. If you distort the cap, failure is not far behind.
Interesting thread. I replaced my front u-joint last Sunday. My T had been giving me a mild "shake" and noise and I couldn't track it down. Went for a drive and it let go a block from my house. Upon inspection, one of the caps was GONE. Don't know how it happened, but they weren't the greaseable type. I had maybe 8,000 miles on the driveshaft and joints. So, I replaced both and feel a whole lot better. On a good note, I'm thankful that my drive shaft was so short. If it had been 2" longer, the results would have been crazy bad.
They did. The attached picture is of what I was told was a 1969 TH400 shaft. By the time I got it, the yoke had been changed out to 27 spline but I had some good high speed service from it. My question is though, 15? I see / saw 45.
Not that this is your problem, but one thing to always check is that the new U-joint pivots very freely in the driveshaft. Too many times U-joints get pressed in place and the press-fit of the caps in the driveshaft will make it feel "stiff" and I remember being told "...they'll loosen up with a little use..", no they won't, they will fail. Then out come your buddies telling you about all kinds of technical reasons the new U-joint failed. If you feel even slight resistance, give a few firm raps with a hammer to the forged ends of the driveshaft until the u-joint moves freely. Sometimes when we press U-joints into place, the ends get "squeezed" together and cause a binding action with the needle bearings.
Dave, How is the rear U-joint failing? is it flogging out or is it splitting at the cross? If you engine is alligned the same as the pinion angle the 2 U-joints both have the same angle If it is splitting at the cross ,90% of the time they split at the grease nipple [zerk, I think you guys call it] This grease nipple must be phased so it is under compression when torque is applied to it. If you phase the cross 90degrees "out" the cross will be under tension and can split at the nipple when torque is applied. A common mistake with hotrodders is to line up the nipples thinking they are in phase [ 1 will be under compression and the other under tension ] This is very critical on IRS 1/2 shafts [eg Corvette ] Please note: I am only refering to the placement of the CROSS ONLY and not the phasing of the whole U-joint [ this mistake is only made during assembly, not when welding the U-joint to the driveshaft ]
That is what happens when you let engineers try to out think themselves! You will notice they don't do it today, so overall it was a failure. I would put them back at 90* out if I rebuilt it. Anybody that doesn't understand phasing of driveshaft u-joints needs merely to grab a couple of u-joints and extensions from their tool box and play with them. It is really interesting to see the speed change every quarter turns and the binding effect it has on the other u-joint if placed out of phase. Another interesting question this has brought up is, what is the effect of having only one u-joint on a torque tube drive shaft? The shaft is in line when static, but is not when hte suspension is traveling up and down. Does this just supply brief periods of pulsed power to the rear axle?
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