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Over the course of the last year, I've been hearing clicking becoming louder and louder from the underside of our Grand Cherokee. I replaced the foremost U-joint a year and a half ago, and have since tugged at all four joins (4WD) to make sure that none of them have any play. I'm out of ideas on what this could be, and I'm not even sure how to go about troubleshooting it.

Some clues that might help...

  • the clicking only occurs when the car is in motion.
  • the frequency of clicking increases with speed
  • the noise has increased in volume over the past 6 months.
  • the noise happens immediately after the car starts to move, even if the car was just started.
  • it seems like the clicking is coming from somewhere near the front of the car, either directly under the gear shifter (which is where the transfer box is) or in the engine compartment (I know, this isn't much help, but it might provide some incite.)

If there's any other detail you'd like to try to get info about, don't be shy. I'm also curious if there's anything in the wheels that I should be looking at...

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Does it make the noise in reverse as well? Can you make the noise better or worse by turning, putting it in 4WD, or anything else? –  Larry Sep 23 '13 at 17:37
    
@Larry Great questions; I'll try these scenarios tonight. –  Lynn Crumbling Sep 23 '13 at 18:49
    
@Larry I posted an answer; it's the transfer case. –  Lynn Crumbling Oct 18 '13 at 18:03
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2 Answers 2

I have found that many times a U-joint in the early stages of failure will still pass the hand powered tug and twist test. It may be one or several damaged rollers that cause the clicking. The only sure method is to disconnect the suspect shaft and pivot the joint by hand to feel for any binding. You can try to isolate which joint is bad by driving slowly and have a second person outside the vehicle locate the area of the noise. As @Larry has asked turn the wheels left and right if possible drive over a small obstacle like a block of wood. The idea is to stress the joint in more than one direction. If it has a CV jointed axle you may not be able to manually feel any play even when the joint is really bad. The typical first symptom is a clicking during hard low speed turns like entering or exiting a parking space. It will get gradually worsen until it clicks constantly while in motion and worse during acceleration.

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+1 Thanks for this -- although it wasn't the problem, it was still incredibly helpful. –  Lynn Crumbling Oct 18 '13 at 18:02
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up vote 1 down vote accepted

The mystery noise was tracked to the transfer case. Even without a load on the car, the noise could be heard coming from the case box when the car was up on a lift and shifted into drive. I'm not sure that I would have figured this out if I hadn't had a mechanic put it on a lift... the alternative would have been to get it up on multiple jacks and craw under it (and I'm not sure that I trust no-name jacks that much.)

I haven't opened up the case yet, and the mechanic just wants to do a full replacement (as opposed to attempting to repair it.) I suspect that when or if I do, I'm going to find a bunch of broken teeth.

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As a post-mortem, I ended up finding a huge hole in the bottom of the transfer case (pushed from the inside-out!) Without any ATF in there, it was getting really noisy. I went to a local salvage yard, got a used NP 231 and put it in, and now it's quiet again.... –  Lynn Crumbling Nov 5 '13 at 17:26
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