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Crrrrrthunk!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MadIrish, Aug 20, 2001.

  1. MadIrish

    MadIrish Registered Member

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    When you throw your tranny in drive an there is the lag time followed by a 'thunk' and a jolt to the driveshaft; is that the Ujoints or the tranny not getting fluid or both? How much slop can bad Ujoints cause?
     
  2. Jonathan

    Jonathan 1/2 ton status

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    Fill out your profile so we can have more info on your truck. I have the same problem and I belive it's a loose chain in the t-case.

    77 Blazer, 350, NP203, K&N, 31-inch Cooper Discoverers
    <a target="_blank" href=http://community.webshots.com/user/jonathandwill>http://community.webshots.com/user/jonathandwill</a>
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    First you need to fill out your profile and let us know what you have.
    Yes U-Joints can cause that thunk. So can worn ring and pinion, bad motor and tranny mounts, slop in tranny, slop in case Exhaust hitting case/frame/body. The 208 case in particular is known for noise from the slip yoke.
    Old trucks let you know there old. If it's not the U-Joints it may just be normal wear.

    It's not my damn planet monkey boy!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>
    75 Jimmy, Dollar
    79 Chevy Blazer, Her's
    70 Chevy Burb
    Grim-Reaper
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Jonathan, the chain in the t-case is only used to provide power to the front drive. So if you're getting the clunk in 2WD, then the chain isn't the culprit. [​IMG]

    Detroit Lockers have a lot of slop in them that can make you think that your entire driveline is about to fall out. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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    It's a great day to be alive...
     
  5. Jonathan

    Jonathan 1/2 ton status

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    I have an np203 so I'm never in 2wd

    77 Blazer, 350, NP203, K&N, 31-inch Cooper Discoverers
    <a target="_blank" href=http://community.webshots.com/user/jonathandwill>http://community.webshots.com/user/jonathandwill</a>
     
  6. Itali83

    Itali83 1/2 ton status

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    My truck with 700r4 and 208 does the same thing, what is it??
    Ben 87 Jimmy
     
  7. SAVAGE1

    SAVAGE1 1/2 ton status

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    Check the simple things first. Check to see if your t case crossmember bolts are tight. Mine were loose and they made a loud CLUNK sound when put into gear. If that's not it, check all your Ujoints. Shake your driveshafts around to see if there is any play. Or have someone shift your truck into Reverse and First while you look under the truck for any movement. Hope this helps

    Rod
    Alameda, CA
    85 K5 6"ProComp 35"Boggers... and it's still not BIG ENOUGH!!
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  8. rampage

    rampage 1/2 ton status

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    I had that problem for years. What I found worked best was to quickly put it in neutral (before reverse engages) for a few seconds to ease tension in the driveline. It seemed to work for me. Finally my spider gears gave out and I upgraded the diff/r&amp;p while I was at it. No more clunk. But I would definetly check the simple/cheap stuff first that was mentioned. Also jack up the rear and see how much play you have in wheels. If everything checks out ok then drive it til it breaks!

    <P ID="edit"><FONT class="small">Edited by rampage on 08/21/01 01:30 AM.</FONT></P>
     

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