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It is a flex joint! It is constantly flexing as the drive shaft turns, there is always miss alignment from the transmission to the rear end, and on cars and trucks were the rear end is bouncing up and down they really get a work out. Less so on an LS because the rear end is fixed and doesn't move with the road. But still there is an out of align condition due to the body flex, the rubber engine and transmission mounts and the rear end is also rubber mounted and even the drive shaft and the flanges are not perfect, so it can not be a solid deal to replace them, because any sort of misalign or shaft wobble would then be put on something else.
actually there is very little "misalignment" in the drivetrain, even when the mounts are dying.
the flex disk/guibo serves to cushion drivetrain shock, and is NOT analogous in function to a traditional U-joint (which can compensate for drivetrain alignment).
I don't believe delrin/poly would work as they are too brittle when loaded up , but I may be mistaken.
An aftermarket hybrid aluminum/poly bushing should work, as they've been used in the BMW world for some time. Though they are much shorter service life than OEM iirc. http://www.revshift.com/product-p/pfx-24v.htm
Hey guys whats up thanks for all the replies and info! but ive gotten back under the ls and checked the flex joints. I could use some new ones and the bolts and nuts on em have a tenancy to come loose. but yea im now convinced that the problem is that the threading for the drive shaft and trans are stripped cause theres play. i got under the ls and had it in neutral twisted (from the rear) the drive shaft and heard the play coming from the front.
It is a flex joint! It is constantly flexing as the drive shaft turns, there is always miss alignment from the transmission to the rear end, and on cars and trucks were the rear end is bouncing up and down they really get a work out. Less so on an LS because the rear end is fixed and doesn't move with the road. But still there is an out of align condition due to the body flex, the rubber engine and transmission mounts and the rear end is also rubber mounted and even the drive shaft and the flanges are not perfect, so it can not be a solid deal to replace them, because any sort of misalign or shaft wobble would then be put on something else.
The diff actually moves a fair amount on the LS, despite being fixed to the body. It is after all supported by rubber bushings. That said, the LS does not see a large amount of drivetrain movement unless you have blown engine and tranny mounts, nor does it see excessive missalignment or wobble in the drive shaft. The whole point of these bushings, also called "hardy discs," is to soften impacts through the driveline. They are not at all designed to take misalignments as they are only used on IRS cars where the diff and drivetrain are essentially pinned to the frame. I have never thrown my digital driveshaft gauge on one of these cars but I would expect less than 1°, probably less than 0.5° of driveshaft misalignment on a car as refiners as the LS.
One symptom of wear on these parts is excessive driveline clash when shifting from park to D/R or between D&R. However the classic "clunk" of a standard u-joint is muffled as it is a rubber connection.
I would wager dollars to doughnuts that the tranny and probably the engine mounts are probably torn through and likely the cause of his problems. The discs might also be fubar'ed but the mounts are likely to be the route cause of the problem.... That and driving like a teenager who stole daddy's keys.
Sorry already installed.
I joined jet.com (free) and with my first purchase discount it was $144.23
Cool, I'll order one when mine bites the dust.
I've done lots of burnouts, super hard pulls almost daily, and lots and lots of snow drifting and my flex disc doesn't look shot at all. You may want to investigate why yours are dying so quickly before your new one shreds.
If mine has some visible cracks developing but I don't yet feel any vibrations, should I go ahead and replace these? I've got 279k on my drivetrain, which I assume is all original.
I live in a super hot and dry environment where it gets to 120 degrees in the summer, so that's why I assume mine "failed" at only 279k, when people would most likely see 500k out of the originals in a less dry climate.
10-30-15, 06:39 PM
