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Discussion Starter #1
07 6mt full time 4wd. So under acceleration I get a loud pop that sounds like it’s coming from the front end. If I stay on the gas it will be a repeated pop until I back off. Sounded like passenger side so I replaced the cv axle but didn’t change anything. I recently pulled the front shaft and greased the slip joint and the ujoints. The ends moved freely and didn’t seem to have any play in them. With the shaft out and in 2wd only there is no noise. So it leads me to believe it’s either in the front end or TC. I’ve seen videos where people talk of a loose TC chain having too much slack and skipping teeth. There is no hum or growling while going down the road so I suspect the front diff is fine. Just changed the fluid in it. Noticed some metal on the magnet but not much so who knows. There is still the driver side cv axle that has excessive grease leaked and wouldn’t hurt to change but I don’t want to just throw parts at it in hopes of repairing it. Has anyone had to replace a tc chain yet? Should I just get a lower mileage unit or do they even make rebuild kits or ever a chain for that matter?
 

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MOAB SUPERSTAR
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Personally I would go ahead and swap CV axles because it’s likely a needed repair anyhow, and if the sound disappears, you have your answer. The TC is very stout and they tend to last a long time - but you did not say what your mileage is...?
 

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Discussion Starter #3
Just over 200k. It feels as tho any power is applied to the front it will start to pop. If I put it in 2wd with the driveshaft in it won’t move but if u roll down my driveway and turn it will pop and bind up. Pull front ds and drives fine. Doesn’t pop when I turn while driving only under throttle and will in almost every gear. Sounds like the front middle under the engine. So ds ujoints or cv axle or front diff or the chain and sound is traveling. I pulled the ebrake and applied power to the engine and didn’t get any noise.
 

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Discussion Starter #4
So just had it at my local 4wd shop. They couldn’t make the sound happen on the lift as apparent it requires resistance. Driving around their lot they were able to determine that it’s coming from the center of the truck and believe it to be the transfer case but are not 100%. Ujoint appear to be fine. I just got back home and pulled the front drive shaft. I thought that I was driving in N before but I was not. I noticed that in H or N it will not move. But in HL or L it will. Basically both of those lock the diff to the case from what I’ve read. I would suspect that even with the ds pulled and still being in 4HL it 4L that the chain is still being engaged. No noise in made when driving like this. I’m starting to wonder if it’s the driveshaft or possibly the front end is just off enough to cause a bind with the case?
 

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I understand you said in sounds like it is coming from the front of the drivetrain. Your description sounds like it could also be in the rear gear also.
 

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Discussion Starter #6
The guys at the shop drove it around and one got under it. Said it is defiantly coming from the center of the truck. Doesn’t make the noise with the front drive shaft out but I’m not sure how the transfer case is working still with no drive shaft attached. I’m tempted to replace the u joints and reinstall to see what happens. It’s become a very hard noise to pinpoint. I’m stumped because it’s not making the noise with the drive shaft out and the transfer case in 4 high lock.
 

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Has anyone actually peeked inside the front diff with a scope?
 

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Discussion Starter #9
No I was going to pop the front cover off and inspect what I can but the noise is coming from the center near the transfer case. The gears make no noise at all driving down the road. When it pops it sounds like a bad U joint or the tc chain skipping. Anytime I locked the gear with the front ds in it would make the loud pop under throttle. The pop depends on the torque load. First gear would pop non stop under heavy throttle. It’s slowly gotten worse to where if the throttle in 4th or 5th is substantial it will even pop. I’m not sure how much torque load the front axle is under when the awd sends more power to it. I can baby it and it won’t pop. With the front ds out and locked in either H or L it won’t pop. With the ds in with all 3 it pops. When it’s locked and I turn with an incline it will bind hard. Lots of unknown for me with this type of tc. Does it need the ds in to put torque on the chain to cause slipping? Could the front diff mount or trans mount be bad and allowing the set up to twist under throttle and either pop inside the case or pop at the ujoint? Or could it be a bad ujoint? Not having much luck trying to diagnose it.
 

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Discussion Starter #10
I’m leaning to it’s the transfer case being awd with 200k miles. I just changed the fluid and it was low and dark. I can source a change for $250 but what other parts would I need to replace? And if they are Toyota only parts I know they won’t be cheap. I can source a 90k mileage tc for $700. Might just go that route and sell this one cheap for someone to rebuild. Going to recheck the yoke splines first slippage to see if any have skipped but when I pulled it the thing felt tight.
 

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Discussion Starter #12
It’s the transfer case chain. Gonna swap out the case with a low mileage unit. All I can think is being AWD puts more strain on the chain and at 200k it’s had enough.
 
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