# "CLUNK" sound when shifting into 4wd



## billt (Feb 24, 2005)

I have a '03 Frontier CC with about 25,000 miles on it. I was wondering if anyone else has had this problem. When I shift from 2wd into 4wd I get a CLUNK sound from the transfer case. If I shift out and back again it seams fine, its only when I initially shift into 4wd.
Thanks,
Bill


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## Zilverado (Sep 25, 2002)

I am not a 4wd expert, but I would assume it's similar to other 4wd I've driven.

When you first shift into 4wd, the transfer case engages your front drive shaft. The "clunk" you hear is this engagement happening (normal) as the shafts slide into alignment. If you shift back into 2wd, the tranfer case disengages, but the free-wheeling hubs on the front wheels keep the front drive lines turning (but not powered by the transfer case). The driveshaft is simply spinning along to keep it "lined up" or "meshed" with the transfer case. When you go back into 4wd, the transition is smoother, because all the gears/splines on the shafts are still in line.

Once you disengage the front hubs (usually by reversing in 2wd), the front drive lines no longer spin, and come out of alignment with the transfer case. Inorder to reengage the transfer case, the shafts again need to re-align - - thus the "clunk" again.

So that's my explanation. I'm sure there are guys here that can explain it better, but that's the jist - - at least how I understand it.


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## billt (Feb 24, 2005)

Thanks, I was kinda hoping that it was normal. Iwas afraid I was going to damage the gears in the transfer case.


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## Zilverado (Sep 25, 2002)

While I do believe that the "clunk" as you describe it is "normal", and happens on our vehicle as well, I always try to take it easy when engaging 4wd. I tend not to go heavy on the gas until after the clunk. If we shift into 4wd (from a stop) and then stomp the gas, the "cluck" turns into more of a "slam" - - not good. While I think newer vehicles like yours tend to maybe shift smoother than older ones, I always like to be as gentle as possible, just to save the wear and tear on the drive train.


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## moymch (Jan 5, 2005)

As a small sound is normal, a loud "clunk" may not be. If you do a lot of off-roading I would check the U-joints on the forward drive shaft. Just my .02 worth.


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## black_knight (Sep 3, 2003)

yeah my 04 does the same thing... it's normal because that clunk is the front driveshafts and hubs all locking and catching up with the rest of the truck. Also if your back wheels are spinning just a little faster than the front ones (low traction) you'll also get a loud clunk as all the wheels are brought to the same speed. I just usually either stop while shifting into 4x4 or do it at under 10 mph while keeping steady on the gas. It's okay... whatever you do don't shift into 4x4 over 25mph!

Later


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