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clunk sound -need opinions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Neil, Jun 25, 2001.

  1. Neil

    Neil 1/2 ton status

    Jun 10, 2001
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    When my '78 K5 comes to a stop, I hear and feel a clunk underneath. I also feel this more when I hit the throttle to start going again. I think it may be a broke tranny mount. Does this sound like anything else I should check??
    Thanks for help anyone!...78 K5 4x4,400sb,AT,stock drivetrain.
  2. newyorkin

    newyorkin 1 ton status Premium Member

    May 8, 2001
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    Los Estados Unitos
    I have some serious clunkage also. I know for a fact my tranny mount is hosed, I just haven't gotten round to fixing it yet. It clunks in turns, starts, stops, shifts...
    A good visual chreck is to look at it and see if it's dried out and cracked. It's on the cross member that runs underneath where the tranny and transfer case bolt together.
    You should also check the motor mounts, cross member bolts, u joints, and u-bolts at the rear. U-bolts especially. I tried about a billion things to make a seperate clunk go away, and then one day while doing brakes, noticed my u bolts were dangling. Tightened em down and the problem went away.
    Do a search on here for "clunk" also. This is a pretty common thing.

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  3. ftn96

    ftn96 1/2 ton status

    Sep 26, 2000
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    Nashville Tn
    What type of T-case do you have? This sounds like the common old worn out slip yoke clunk. If its a 208 then I would bet $10 to a donut that that is what it is. What this is, is where your driveline is going so fast in one direction adn then when you apply brakes it forces the slope from the worn out slip yoke to go hard in one direction, sort like binding up, then when you release the brake and give it gas it goes hard to the other end of the slope.
    If this is what it is, you can pack some good sticky grease inside the slip yoke then slide then re-install the driveshaft. This will give you a few hundred miles of peace and quite. But the grease tends to run off after a while and it comes back.

    You definately need to check your tranny mount. But most tranny mount related clunks come at take off, but thats not to say that you cant get a downward clunk as well.

    Get someone you trust to get in and put it in drive , hold the brake down and goose it a couple of times and see if the tranny jumps up and down. It will a little with a good mount but you will be able to tell.

    Hope this helps.

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  4. Depdog

    Depdog 1/2 ton status Author

    Feb 17, 2000
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    Could be any one or all of whats listed below, could also be a U joint. If you replace the Tranny mount, might look at doing your motor mounts as well unless they are new, especially if you replace them it with a poly one. I replaced my shot out rubber tranny mount with a poly one and did not do the motor mounts at the same time. Broke the adapter between the tranny and tcase because the motor would touqe over on its mounts but the new poly tranny mount did not give as much so the foot broke off.


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