04 Rubicon Ratcheting Noise Under Heavy Drivetrain Load

Accelerometer

Accelerometer

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San Mateo CA
So I have a 2004 5 sp Rubicon on a 3.5" lift and double cardan drive shaft. Over the weekend I took it on the actual Rubicon Trail here in CA and got to put it through its paces. About half way through the trail it started exhibiting a ratcheting noise anytime I would wedge the Jeep up against a rock to climb and give it gas. At first I thought I destroyed the ring and pinion on one of my diffs but it seems to operate relatively normally outside the rear locker not engaging.

Additional Info:
  • Rear locker light is solid and saying its engaged but the diff performs as if it was open. Confirmed by one spinning wheel in loose traction situations
  • Front locker light is solid and working correctly
  • The ratcheting sound happens regardless of the lockers being engaged or not.
  • The sound only comes up when there is a big load on the drivetrain ie. .climbing up a rock. It does not make sounds when just driving forward.
Has anyone experienced something similar? Did I grenade my rear locker or spider gears? I'm trying to zone in before starting to rip everything apart.
 
Probably the gear based limited slip in the rear axle blew, it's pretty common. Especially if you kept the rear locker unlocked during slippery sections on the trail.
 
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Jerry Bransford said:
Probably the gear based limited slip in the rear axle blew, it's pretty common. Especially if you kept the rear locker unlocked during slippery sections on the trail.
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That is what I was thinking too, the funny thing is I kept it locked the entire trail. If it failed would that prevent the rear from locking up?
 
Accelerometer said:
That is what I was thinking too, the funny thing is I kept it locked the entire trail. If it failed would that prevent the rear from locking up?
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A broken Rubicon LSD doesn't ratchet. It violently cracks and snaps during turns. It behaves like a locker randomly being turned on and off as it continues to break apart. You will feel it when the Jeep bucks and hops when turning. Straight line driving is the same as normal driving.
 
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First thought is axle wrap when loaded up. The ratchet noise is coming from the driveshaft binding u joints as the pinion raises.

Improperly adjustabled, loose, or squishy bushing control arms can allow this to occur.
 
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jjvw said:
First thought is axle wrap when loaded up. The ratchet noise is coming from the driveshaft binding u joints as the pinion raises.

Improperly adjustabled, loose, or squishy bushing control arms can allow this to occur.
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This is a good call and may explain why I only get this noise when pinned against rocks. Ill give all of the control arms a once over.
 
bluescapegoat said:
Sounds to me like a slipping transfer case chain.

Does it do it in 2wd?
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That sounds like a possibility for sure. Not sure if it occurs in 2WD I should have tested that while I was on the rocks. Ill see if I can mimic some of these conditions in an urban environment and report back.
 
Andy-WhiteTJ said:
What ever it is, I would say to take off the diff cover and inspect just in case it's in the differential.
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Yup, going to have to pull it all apart either way since the locker seems to be broken so might as well start there.

I'm starting to suspect they are two separate issues.
 
I had a real loud knock/ratchet sound when my control arm bushings were shot. It was allowing the driveshaft to move considerably which would put the ujoints in a bind. I dont think I have a video of that though...

Another ratcheting sound I experienced once was the centering pin on my rear driveshaft was damaged, the centering yoke was then binding. A local driveline shop offered to repair it, but it was something like $200. I ended up replacing the whole shaft with new spicer ujoints and H-yoke for $300 from Tom Woods.
 
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Well tracked down the sound finally, it’s my radiator fan hitting the bottom of the fan shroud.

A bit strange since I don’t have a body lift or MML. The only thing I can think of is that I tweaked the stock xfer skid enough from rock strikes that it pushed up the transmission and angled the engine enough to do this. Any thoughts?

IMG_8861.jpeg
 
tworley said:
Does the fan wobble when there is an engine load?
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I dont believe so, I checked for play. There is a significant difference in clearance between the top of the shroud vs the bottom. I think I have 1.5" of clearance at the top and maybe 1/8" of clearance at the bery bottom.
 
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