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Drivetrain Clunk...!

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by jimmup, Feb 26, 2002.

  1. jimmup

    jimmup Registered Member

    Joined:
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    Hello,

    I am trying to narrow down the cause of a clunk that I am experiencing in my 72 GMC Jimmy. I have a turbo350 tranny with the standard np205 t-case. the clunk is very consistent when I am at acomplete stop and then accelerate, as well as when I am braking and almost reach a complete stop. To try and avoid having the clunk be really harsh i anticipate when a light is going to turn gree and let off the brake and let the load frokm the motor get me started before I manually accelerate by putting my foot on the throttle. Also, I don't think it is the rear differential becuase the clunk will occur after the vehicle is already moving forward.

    So far I have:
    1) replaced my u-joints
    2) replaced the rear strap yoke connecting the driveline to the rear diff
    3) installed new gears and verified correct backlash at the rear differential

    I am starting to think that it might be a t-case or tranny problem. I did have my t-case rebuilt but no hard parts were swapped. Anybody have any thoughts? If it is the t-case or tranny how do I tell which one has the slop or is causing the problem?

    Thanks!
     
  2. wrath

    wrath 1/2 ton status

    Joined:
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    Location:
    Grayling,Michigan
    The problem I'm having with our '97 Tahoe is identical ..get about 5-10 feet after letting off brake and then it clunks..pull up to stop and it clunks..had it into the dealership and they informed me my carrier had about 1/4 of play in it..they told me my ring and pinion was good .. for $900+ they'll replace the carrier..I havent done it yet ..want to get a second opinion..but you may want to have that checked out..only cost me for lube and a gasket..good luck

    70K5 350ci.350/205 "PROJECT 40"BOGGERS" It runs and its clean !!
    <a target="_blank" href=http://communities.msn.com/OurMudToys/the70k5blazer.msnw>http://communities.msn.com/OurMudToys/the70k5blazer.msnw</a>
     
  3. ErikH

    ErikH 1/2 ton status

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    Location:
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    After replacing the u-joints, I was able to rid my drivetrain of a loud clunk by replacing the entire driveshaft... it was the slip joint that had gone sloppy, nothing else... I wouldn't have guessed it.
    -Erik
     
  4. ntaj*ep

    ntaj*ep 1/2 ton status

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    Location:
    Evergreen state
    jimmup, My first question is, when the new gears were installed on your old carrier did you inspect the assembly? If it is a posi. and it's still orignal (gov-lock style) that is most likely your issue. If the carrier is an open style than the hole that your cross shaft is secured to must be round, and the spider gears also need to be inspected. All this is an assumption on my part that your 1/2 ton running gear is being used...also if your running a lift, and it is using blocks in the rear your axle could put more leverage on the springs and could have cracked a leaf or broken the centering pin on the pack. There are many reasons for that type of clunk so let me know what you find, I've got tons more ideas to "help" you out...good luck, and if you do still have the gov-lock in place I have some other options that will not cost you $900.00!!

    The Red Beast
     
  5. LKJR

    LKJR 1/2 ton status

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    Location:
    Lubbock, Tx
    Clunks are something that is hard to diagnose over the internet, much easier in person, but you may look at the following....when you replaced your u-joints did you rebuild the cv joint as well? Also could be your tcase or tranny like you said, my tcase was clunking, but I don't know why just yet my kit is on the way... sorry I couldn't help more

    Like em big and topless
    You call THAT...a 4x4....LMAO?
     

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