# Can of Marbles - only while in gear

**URL:** <https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107>\
**Category:** Maintenance/Repairs\
**Created:** [October 23, 2008, 6:34am UTC](https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107 "2008-10-23T06:34:31Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Lets\_Just\_Walk](https://avatars.discourse-cdn.com/v4/letter/l/53a042/32.png) [@Lets\_Just\_Walk](https://community.cartalk.com/u/Lets_Just_Walk)\
**Post date:** [October 23, 2008, 6:34am UTC](https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107/1 "2008-10-23T06:34:31Z")

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Hello all you wise auto people…  
  
  
  
 My 1999 Chevy Suburban K1500 4WD has recently developed a noise that sounds like a can full of marbles being shaken.  
  
  
  
 I have read many posts both here and else where (sorry Tom and Ray) and most surmise that;  
  
 - Catalytic converter may be bad  
  
 - Timing issue  
  
 - Low octane ping  
  
 - Loose Heat shield  
  
  
  
 The fly in the ointment is that this sound only happens when I am accelerating in gear. It mostly stops when I coast. The sound stops if I shift into neutral, even if I give it gas. So I am assuming that it shouldn?t be any of the above.  
  
  
  
 The sound is coming from under the car and since it only happens while driving I can’t be more accurate.  
  
  
  
 No work has been done recently and the only observation is that I noticed a few drops of fluid on the driveway under the rear differential.  
  
  
  
 Any help you all might have would be greatly appreciated!

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**Author:** ![rocketman](https://avatars.discourse-cdn.com/v4/letter/r/eada6e/32.png) [@rocketman](https://community.cartalk.com/u/rocketman)\
**Post date:** [October 23, 2008, 11:31am UTC](https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107/2 "2008-10-23T11:31:58Z")

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My vote is for low octane ping . . . check the ignition timing also. The CAT going bad in a '99 is unlikely, but possible. A loose heat shield is easy enough to check, get on your back and shimmy under this truck . . . you won’t even need to jack it up. Good luck! Rocketman

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**Author:** ![researcher](https://avatars.discourse-cdn.com/v4/letter/r/edb3f5/32.png) [@researcher](https://community.cartalk.com/u/researcher)\
**Post date:** [October 24, 2008, 5:34pm UTC](https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107/3 "2008-10-24T17:34:09Z")

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Check your fluid levels in the transmission (if this is a manual), the transfer case, and the rear and front differentials. It sounds like you might be losing a bearing in one of these units. It has to be a bearing that loads under engine torque.

Hope that steers you right.

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**Author:** ![lenjack](https://avatars.discourse-cdn.com/v4/letter/l/f475e1/32.png) [@lenjack](https://community.cartalk.com/u/lenjack)\
**Post date:** [October 25, 2008, 2:43am UTC](https://community.cartalk.com/t/can-of-marbles-only-while-in-gear/21107/4 "2008-10-25T02:43:49Z")

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My vote is for spark knock (octane ping).