# 4wd clunk



## jb1390 (Sep 23, 2008)

I have a clunk coming from a 2002 duramax with 149000 miles when in 4wd. The clunk sounds like a 2x4 snapping under the truck. U joints are fine, and it does not sound like cv's when i am standing outside the truck (coming from further underneath the vehicle). 

The truck has an allison 1000, and I believe a 263xhd transfer case. 

Does this sound like an internal problem-possibly a skipping chain? 

Is there any way of diagnosing this further (safely)?

I can consistently get the noise when I hammer on the pedal, if I take it real easy, I can get it to act just fine. I cannot drive at high speed without the noise (tried tonight in the snow). 

I have done some reading on pump wear, etc. A rebuilt t-case (if that is what it is), runs about $1400. The parts are quite a bit cheaper, but I am not sure how easy of a job it is. Anyone with a similar issue want to chime in?


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## carkey351 (Oct 18, 2010)

jb1390;1333935 said:


> I have a clunk coming from a 2002 duramax with 149000 miles when in 4wd. The clunk sounds like a 2x4 snapping under the truck. U joints are fine, and it does not sound like cv's when i am standing outside the truck (coming from further underneath the vehicle).
> 
> Does this sound like an internal problem-possibly a skipping chain? Maybe... http://www.dieselplace.com/forum/showthread.php?t=435948
> 
> ...


 If you can rebuild an automatic transmission, a T-case is similar in difficulty (easier in my opinion).


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## jb1390 (Sep 23, 2008)

I've never touched the inside of a tranny-always limited myself to motor/other vehicle stuff. 

If it's that tough, perhaps a rebuilt is the way to go. 

Any chance I missed something and this could be something other than the transfer case?


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## kimber750 (Sep 19, 2011)

No noise in 2wd? Going straight or turning? I would check everything noises can be hard to find, could sound like it is coming from the back when really it is the front. Had a noise on an old jeep I had every time I hit a bump. Sounded like it was coming from under drivers seat. Searched for years to find it, finally figured out it was one of the hood hinges.


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## jb1390 (Sep 23, 2008)

No noise at all in 2wd. 

I had my wife drive it, while I stood outside, and the noise is not coming from the cv's. 
I repeated that test with a friend standing outside while I drove it. Same diagnosis. 

It does not matter if I am going straight or turning. The noise happens when it is under load. If I accelerate, it pops. If I drive slowly forward on dry pavement, eventually it pops. If I drive slowly on soft ground, sometimes it doesn't pop. 

I will drain the oil in the t-case as one more check.


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## Triple L (Nov 1, 2005)

My rig was doing the same thing... Its not the trans, I have an ATS extreme in my truck, we've came to the conclusion that its coming from somewhere by the transfer case support crossmember... What it is I have no clue, My truck does it in 2wd, if I take off hard, crack, then stop nothing, but put it into reverse then it cracks... I almost think its a box mount or something but havent had the time to really dig into it... It seems to have stopped now all the suddon and I dont know why...


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## BlizzardBeater (Aug 29, 2010)

Just to to be a pain in the butt, I recommend you really take a look at the two U-joints on the axle driving the front differential. If you're absolutely positvie thats not it, check your tranny mount.


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## kimber750 (Sep 19, 2011)

BlizzardBeater;1334302 said:


> Just to to be a pain in the butt, I recommend you really take a look at the two U-joints on the axle driving the front differential. If you're absolutely positvie thats not it, check your tranny mount.


X2 they may not be loose but bearing could be frozen and won't be long until a failure.


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## 2COR517 (Oct 23, 2008)

Do you have matching tires front and rear?


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## jb1390 (Sep 23, 2008)

So........I have a small hole in the side of the t-case. For anyone interested in reading more, check out 263xhd pump rub. Looking for a rebuilt case. Merchant automotive seems to be a decent price, and comes with a lifetime warranty against pump rub problems.


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