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Clunk!

Discussion in 'GM Powertrain' started by markman34, May 19, 2010.

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  1. markman34

    markman34 Member

    Hi Everyone,


    I'm just hoping to find out any information on my problem before taking my truck to the dealer for some hopefully warranty work.
    I have the 07 NBS VortecMax crewcab truck with just shy of 100,000 km on it. My problem is that I have a lot of drive-line play which results in a clunk.
    I get a clunk when shifting from R to D. I get a clunk when coasting followed by engaging the throttle. The thing is clunking a lot.
    I looked underneath and there is significant play in the drive-shaft. After inspecting a few other identical trucks that had absolutely no play in the drive-line, I think I have a problem with mine.
    Does anyone have any idea what is considered an acceptable amount of play? I know that GM will tell me that there is nothing wrong with the truck and I'm screwed.
    Have there been any service bulletins or recalls relevant to play in the drive-line?
    Any help you have to offer would be appreciated.

    Thanks in advance.

    Mark
     
  2. silverado00

    silverado00 New Member

    i have the same problem, its in the tranmission, to much clearance in gears. i have had 3 trannys put in mine. the last tranny dont clunk anymore. So hard to say if i would worry about it or not. I think you should be alright.. Also yes there is a buelltin on it.
    Condition
    Some customers may comment on a clunk, bump or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop.
    Cause
    A slip/stick condition between the transfer case output shaft and the driveshaft slip yoke may cause this condition.
    Diagnostic Tips
    There are several resources in the electronic Service Information System which can provide the technician with information on diagnosis and repair of clunk conditions, and fix the customer's vehicle right the first time without unnecessary parts replacement. Some of the documents available in SI include:
    ^Symptoms - Propeller Shaft
    ^Knock or Clunk Noise
    ^Rear Drive Axle Noises (SI Document ID #700580)
    ^Launch Shudder/Vibration on Acceleration (Replace Propeller Shaft and Install a New Pinion Flange/Seal), Bulletin # 02-04-17-001
    ^Information on 2-3 Upshift or 3-2 Downshift Clunk Noise, Bulletin # 01-07-30-042
    ^Driveline Clunk When Stopping (Reprogram Powertrain Control Module (PCM), Bulletin # 03-07-30-028

    Correction
    Replace the rear drive shaft slip yoke with a new nickel-plated slip yoke
     
    Last edited: May 22, 2010
  3. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    So you can twist the driveshaft an excessive amount? This is with the rear tires on the ground and the transmission and/or transfer case in neutral?

    Sounds like your rear diff is worn. Could be excessive R&P backlash due to worn gears, worn carrier bearings, or a worn carrier. Most likely, a little of all.

    I would pull the diff cover and look around. To get the best feel of the diff, I take the rear tires off, and remove the driveshaft from the yoke.
     
  4. markman34

    markman34 Member

    thanks for the replies.

    I have had another look at the play in the shaft and noticed that there is no play with the parking brake on but a bit of play with the brake off.
    This makes me believe that there is play in the output shaft on the transfer case and not the diff.
    Any thoughts?
    I'm taking the truck in to the shop for it's final look over before the warranty expires tomorrow.
    Wish me luck.

    Marko
     
  5. markman34

    markman34 Member

    Took the truck into the dealer today and they said they fixed the clunking problem.
    Apparently, they have re-programed the computer, replaced one u-joint, and repacked the grease in the splines for the shaft coming out of the transfer case.
    I have not noticed any difference yet but will be keeping a close eye on it for the next few days.

    Thanks for all your help everyone. I'll keep you posted.


    Marko
     

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