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Vibration under deceleration and a large thump under acceleration

Discussion in 'The Garage' started by juanblzer, Apr 19, 2004.

  1. juanblzer

    juanblzer 1/2 ton status

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    alright:
    I have a np208 and i had a bad vibration before I swapped in a 1350CV by Highangledriveline. Within the last couple of mmonths I have heard the t-case hit the floor under acceleration (when the truck shifts into second gear). Withing the last couple of weeks I also noticed a severe vibration/whine under deceleration. I chocked the tires and put the truck into drive and noticed that the driveshaft has some play by the slipyoke of the NP208. I have an extra 208 (so I am not swapping in a 205 and 203)

    Does anyone have any ideas? THe shaft was bought around Sept-Oct of this school year. Warranty? Is it the case? Worn splines? F-d up bearing?
     
  2. BlazerGuy

    BlazerGuy 3/4 ton status

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    What do the t-case mounts look like?
     
  3. juanblzer

    juanblzer 1/2 ton status

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    well, my t-case crossmember is a custom tube unit. It runs poly bushings on the framerail mounts and a factory t-case mount that actually bolts into the t-case/crossmember. The factory mount feels pretty soft. the polymounts are chewed up on their edges from crawling.
     
  4. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    I wonder if the adapter is broken? /forums/images/graemlins/dunno.gif
     
  5. juanblzer

    juanblzer 1/2 ton status

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    it doesn't really leak though...
     
  6. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Mine was doing something similar. Right after I installed CV shaft I still had an issue. Turns out my pinion yoke on rearend was loose. Someone must of loosened it at the junkyard I got my 12 bolt from, like they were going to get the yoke. I never checked when axle installed and that was my problem. Don't think it is your problem , but it wont hurt to check it out the play in the yoke. /forums/images/graemlins/k5.gif
     
  7. juanblzer

    juanblzer 1/2 ton status

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    will do!
     
  8. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Does your adapter bolt to your crossmember? One or both of the "feet" could be broken. This happened to me on a 82 GMC with a NP208. Since you said the t case hits the floor Im thinking something other than a worn driveshaft is going on....
     
  9. juanblzer

    juanblzer 1/2 ton status

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    could you explain "feet"?
     
  10. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    [ QUOTE ]
    could you explain "feet"?

    [/ QUOTE ]

    Jeff isn't online now , but I believe he meant the pads that sit on crossmember and the trans mount bolts thread into.

    Also when you said transfercase was hitting floor, did you mean it literally , or just sounds like it? /forums/images/graemlins/k5.gif
     
  11. juanblzer

    juanblzer 1/2 ton status

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    feels like it, its a pretty hard thump...
     
  12. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    [ QUOTE ]
    feels like it, its a pretty hard thump...


    [/ QUOTE ]

    Well then double check everything mention in this thread. Don't forget to check motor mounts either. Soemtimes the mounts if they are factory rubber will be real mushy and let things move. Check your yokes and u-joints. Also don't overlook the obvious, you could of lost a weight from the shaft if you smacked a rock or something. /forums/images/graemlins/k5.gif
     
  13. unclematty

    unclematty 1/2 ton status

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    first thing first, check all you mounts, engine trans t-case
    then look for any cracks in crossmembers and check all driveshafts for loose or broken yokes the sound you describe makes me think of something shifting position acording to whatever torque is place against it so look for things thatcould move under load /forums/images/graemlins/thumb.gif possibly even your exhaust pipe, ive seen it happen
     
  14. R72K5

    R72K5 Banned

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    yep check U joints and all mounts holding drivetrain to chassis
     
  15. juanblzer

    juanblzer 1/2 ton status

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    okay update!

    I have ORD motor mounts (they are poly and look in decent shape). Last night I took a floor jack and used some pieces of wood and jacked the tranny up. There is some play in the rubber mount that attaches the crossmember to the adapter. OTher than that I really couldn't "see" any damaged or broken pieces. Some of my body mounts have seen better days, Would this make a difference? I'll check exhaust clearance. Any other ideas. I have a buddy who owns a tranny shop. Perhaps I'll take it by.
     
  16. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    [ QUOTE ]
    There is some play in the rubber mount that attaches the crossmember to the adapter

    [/ QUOTE ]

    I would replace them anyway. I hear you should run poly to match the motor mounts. How much play do you have? When I replaced mine they seriuosly looked and felt like black marshmallows !! If you can get it to that shop for free go for it. A lift helps a lot. /forums/images/graemlins/k5.gif
     
  17. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Yes, having a shop look at it might be a good idea, if the t case is actually moving enough to hit the floor the problem should be obvious.
     

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