Clunk When Disengaging 4x4
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More Turbo
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More info. Having trouble getting 4x4 to engage also. Finally locked the hubs manually and it engaged. 4x4 light comes on when it’s enfaged or not. Could be coincidence that it finally engaged but I suspect something with the hubs. Could they clunk badly when disengaging even when 4x4 wasn’t working?
Logistics Pro
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If your 4wd switch lights up and you’re hearing a clunk, I’d say your transfer case is engaging.
When you say it’s not engaging until you manually lick your hubs, that (to me) simply means that your vacuum for the automatic locking hubs has died.
If that’s true, simply manually lock your hubs for the winter and continue to engage the 4wd as needed.
That’s what I do on mine.
Regarding the clunk noise, I’ll occasionally get that too; it’s not loud.
When you say it’s not engaging until you manually lick your hubs, that (to me) simply means that your vacuum for the automatic locking hubs has died.
If that’s true, simply manually lock your hubs for the winter and continue to engage the 4wd as needed.
That’s what I do on mine.
Regarding the clunk noise, I’ll occasionally get that too; it’s not loud.
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More Turbo
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Mine was horrendously loud and I could feel it. I’ll try switching to 2wd with the hubs manually locked but honestly it scares me that something is going to bust. Nothing abnormal when switching to 4x4.
Fleet Mechanic
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From: West by God Virginyuh
I’ve never had a clunk in any of my trucks when switching into or out of 4x4, so something is definitely wrong. I’d guess it’s in the transfer case. Can you tell if the clunk is coming from below, slightly behind your seat? Does it happen if the steering wheel is completely straight? Just checking to see if maybe you have the system loaded when disengaging, but even then I think you’d be hearing/feeling the front tires chirping before you feel the clunk.
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More Turbo
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Tested it tonight and it shifts smoothly and flawlessly in and out of 4x4 with the hubs locked. Guess it’s something to do with the hubs but I don’t know enough about how the whole 4x4 system works to know what was going on. Guess it’s a summer project of new hubs.
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Fleet Mechanic
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From: West by God Virginyuh
Man, that’s weird...I can’t imagine the hubs failing in a way that would cause the loud clunk you’re describing. Please post a follow up to let us know if new hubs fix the issue!
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More Turbo
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What happens when the transfer case engaged but not the hubs? How about if 1 hub engaged and not the other? Can there be partial engagement? I don’t know about any of it other than there was a horrendous sound that’s not there now that the hubs are manually locked. Would love to hear some ideas. Hopefully it wasn’t my front diff chewing off gears..... 😬
Fleet Mechanic
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From: West by God Virginyuh
If the transfer case engages but the hubs don’t, then basically your front axles are turning and also spinning the inner portion of the hubs that are in contact with the end of the axle.
So now that I think about it some more, maybe it’s possible that a hub HAS gone bad, and somehow the portion of the hub that locks together is making that clunking noise. Strange that it would do it only when disengaging, though.
When you engage 4x4 does your climate control go to defrost? That would indicate a vacuum leak in your 4x4 shift on the fly system (would only affect hub actuation, not transfer case) which is why it doesn’t seem to engage. Only your transfer case would engage, the hubs wouldn’t lock.
So now that I think about it some more, maybe it’s possible that a hub HAS gone bad, and somehow the portion of the hub that locks together is making that clunking noise. Strange that it would do it only when disengaging, though.
When you engage 4x4 does your climate control go to defrost? That would indicate a vacuum leak in your 4x4 shift on the fly system (would only affect hub actuation, not transfer case) which is why it doesn’t seem to engage. Only your transfer case would engage, the hubs wouldn’t lock.
Fleet Mechanic
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From: West by God Virginyuh
So, if you have your fan on HI blowing out the dash vents, then switch into 4x4 the air stays blowing out of the dash vents?
If there’s a vacuum leak in the ESOF system it’ll only affect the climate control when you switch into 4x4. They’ll work normally otherwise.
If you switch into 4x4 and it doesn’t go to defrost then something is definitely wrong with the hubs, or the vacuum line is capped off or blocked...because that would mean no vacuum leak but the hubs aren’t locking.
If there’s a vacuum leak in the ESOF system it’ll only affect the climate control when you switch into 4x4. They’ll work normally otherwise.
If you switch into 4x4 and it doesn’t go to defrost then something is definitely wrong with the hubs, or the vacuum line is capped off or blocked...because that would mean no vacuum leak but the hubs aren’t locking.
Fleet Mechanic
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From: West by God Virginyuh
Got it. I’m guessing, unless your lines are capped off, that the hubs are jacked up since you said 4x4 only works when you manually lock them. Still not sure what would cause the clunk even if the hubs were partially engaging. Unless they are partially engaging and the clunk is coming from the hubs themselves when that disengage vacuum pulse hits them. But it’s not a strong vacuum pulse, so...I give up. 
Hopefully the new hubs solve the issue!
Hopefully the new hubs solve the issue!
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