I got bad vibes, man- FIXED. Go to page 9

1 week and $200 in parts and 2 hours of my life later, it's not fixed.
Replaced the motor mounts and tranny mount (age and seeing some play in driver's mount) with OEM ones (same as what it had prior) with zero difference.
Called @jeepinmatt and had a long, engineer-type conversation. We came up with a theory the rear yoke may be "off" and when the one driveshaft that ran smooth (but too short) was indexed on it, they somehow mated perfectly. So, I just swapped a new Yukon yoke on the rear- no different whatsoever.

The "good" shaft that had zero vibes is the one I dropped off at a local driveline shop to be retubed, so I don't have it as it was anymore. Otherwise, I'd have added a limit strap and rocked out.

I am replicating this on jackstands, at ride height, in 2wd. Swapped tires front to back just to see- no change. Swapped random driveshafts I have here- no change. Does not do it w/o a driveshaft in.
Andy at Ironman said the Rusty's UCA bushings (OEM style FVWIW) are notiously soft and could *possibly* be allowing the diff to rock even with a balanced shaft. Can't hurt, but I'm kinda done throwing parts at it.

This is absolutely infuriating.
 
Jody Treadway said:
I got $5k in driveshafts, lol
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sick.jpg
 
Jody Treadway said:
Correct. Rear axle and/or driveshaft must be spinning
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Could you devise something to spin the rear tires up to speed with no driveshaft in? Either something spinning the pinion and remove when up to speed, or something turning against a tire to spin it? Like a dyno drum that spins the tire instead of tire spinning dyno.
 
LBarr2002 said:
Could you devise something to spin the rear tires up to speed with no driveshaft in? Either something spinning the pinion and remove when up to speed, or something turning against a tire to spin it? Like a dyno drum that spins the tire instead of tire spinning dyno.
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I've thought the same thing. Or a way to disconnect the driveshaft and spin just it.
I haven't devised a way to do either as of yet
I did consider locking down the rear suspension and retesting. Seeing if I can rule out the UCA bushings by placing a pipe wrench around the tube and jacking up the handle (to keep it from rocking).
I'm curious if the housing rocking is the chicken or the egg.
 
Any chance a just slightly bent axle housing or axle would cause this vibration. Totally spit balling here, BTW.
 
Jody Treadway said:
I've thought the same thing. Or a way to disconnect the driveshaft and spin just it.
I haven't devised a way to do either as of yet
I did consider locking down the rear suspension and retesting. Seeing if I can rule out the UCA bushings by placing a pipe wrench around the tube and jacking up the handle (to keep it from rocking).
I'm curious if the housing rocking is the chicken or the egg.
Click to expand...

Could you pull the axle shafts and have the driveshaft just spin the r&p? Not sure that it would change much, from current, with the axle being of the ground.

Or take the ring/carrier out and just have the pinion & driveshaft spin. Couldn't run long as it wouldn't be getting oil.

Does the vibration change if the driveshaft angle changes? Like drooping or compressing the suspension 2".
 
Has the R&P been changed in any of these 10,000 tests?
 
paradisePWoffrd said:
Could you pull the axle shafts and have the driveshaft just spin the r&p? Not sure that it would change much, from current, with the axle being of the ground.
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It would be a PITA and I'm not confident it would do much
paradisePWoffrd said:
Or take the ring/carrier out and just have the pinion & driveshaft spin. Couldn't run long as it wouldn't be getting oil.
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It takes 50-65 mph to get there, I'm weary of trying that
paradisePWoffrd said:
Does the vibration change if the driveshaft angle changes? Like drooping or compressing the suspension 2".
Click to expand...
Haven't tried it with the suspension drooped or moreso compressed. Subtle pinion angle changes don't have any effect
 
Ron said:
Has the R&P been changed in any of these 10,000 tests?
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Have not changed it since regearing it back in the day. Pattern was and still is great. Backlash is consistent all around the gear. No runout on the exposed machined end of the ring where it mayes up to the carrier
 
is the driveshaft racist?
 
Bebop said:
Change rear axle and re-try?
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I'm willing if I can locate a complete ZJ rear axle assembly.
I just can't see where it how the ring and pinion can be a cause. I know 100% the preload, pattern, backlash and overall condition are all ideal.
I'll probably call ecgs tomorrow and chat with Chase a bit.
 
Have you considered a West Virginia rehab?

Whole lot of Cherokars out there to fight with this one so much
 
Jody Treadway said:
I'm willing if I can locate a complete ZJ rear axle assembly.
I just can't see where it how the ring and pinion can be a cause. I know 100% the preload, pattern, backlash and overall condition are all ideal.
I'll probably call ecgs tomorrow and chat with Chase a bit.
Click to expand...

Just upgrade. Or, pull the axle out of mine and upgrade mine! Keep the axle as payment :D
 
JSJJ388 said:
Just upgrade. Or, pull the axle out of mine and upgrade mine! Keep the axle as payment:D
Click to expand...
If I really thought it was in the rear diff, I'd take you up on it.

I just hung up with @Lee at ECGS who was gracious enough to give me 20 minutes of his time. We discussed everything and came up with....it's gotta be the rear driveshaft. The fact that one random shaft fixed it proves this fact. Mathematically, I see no way I have gotten 4-5 "bad" driveshafts. But it's gotta be.
 
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