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Pulsating Vibration

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mountainexplorer, Sep 18, 2002.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    When I'm going down the highway over 50 mph, I start to hear and feel a pulsating vibration that seems to be coming from the tranny/T-case area (TH350/203).

    When I let off the gas, the pulse is slower, and when I step on the gas to go up a grade, it pulsates faster. Could it be something with the torque convertor?
     
  2. milspecjimmy

    milspecjimmy 1/2 ton status

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    i almost want to say u joint or drive shaft balance, of course its hard to tell with out being there
     
  3. mountainexplorer

    mountainexplorer 1/2 ton status

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    I thought it would be the rear driveline or a U-joint, or even the rear end at first, but if I put it in neutral while cruising along at 55 or 60, it stops doing it.
     
  4. twenty_below0

    twenty_below0 1/2 ton status

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    defanetly check the drive line and also I have had similar vibes but it was a wheel weight that had come off, so some thing to check out, also check to see if your t-case mounts are good, poly mounts helped mine out quite a bit.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't think I'd blame the torque converter, it spins at engine RPM all the time, and if anything was wrong with it, you'd probably know.

    Anything short of catastrophic converter failure, usually its rattling or whining noise in park/neutral resulting from worn out bushing/bearings in the converter.
     
  6. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    mine does that too and it didn't start till I put the TH400/241 combo in after I blew up the 700/208 combo. My dad's '79 2wd truck with a TH400 does it too and my G/F's folks' '86 burban with a 700R4 does it too so I don't know if it is anything bad orjust common for A/Ts to do that
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Pulsates or whines? If they all pulsate, I'd for sure check the tranny and engine mounts. I have a feeling tranny mounts are one of the most overlooked problem in RWD vehicles.
     
  8. laketex

    laketex 3/4 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    When I'm going down the highway, I start to feel a pulsating vibration....

    [/ QUOTE ]


    Dont complain, some people pay money for that!
     
  9. mountainexplorer

    mountainexplorer 1/2 ton status

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    It doesnt whine. I can literally feel a vibration through the whole truck come in and out. It didnt do it before. The 203 that was in it broke a chain, so I put in another 203 and rear driveline that was out of a driving truck. Ever since, it has done this. I wouldnt be too concerned if it wasnt as loud/intense as it is. I know it's running at high RPM's at 55-60 (4.10 gears with stock 9.50-16.5 tires). I was going to swap 3.73 gears in before I sold it if I couldnt find anything wrong with the tranny/T-case.
     
  10. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    it's a vibe like this
    .....dadadadadada........dadadadadada........dadadadadada....... that you can feel in the floor. No sound involved. I haven't checked motor mounts but they are the same as with the 700 but my mounts for the tranny/t-case are the ones that came with the new tranny. I already sold my old crossmember otherwise I could put that one back on and see if it helps but I don't really see how ti could be that.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    The driveline that was out of another truck...do you know if it had a vibration too? If you don't know, I can't think of the name of it, but is the center of the shaft splined? (no slip yoke, right?) If it is, make sure the u-joint caps line up at the front and rear of the driveshaft.

    I'm fairly certain I know what kind of vibration you are talking about, its the kind you can hear/feel in twin engine planes and boats, right? You can hear them sync up and then get out of sync over and over..only reason I suspect u-joints. Wild guess of course, but other than out of balance tires, I don't know what would cause it besides driveshaft/u-joints.
     
  12. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    I used my old drive line in teh new tranny/t-case and it is slip yoke anyways and didn't have the vibe before the tranny swap.
     
  13. mountainexplorer

    mountainexplorer 1/2 ton status

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    Its a definite vibration you can hear. The transfer case and driveline came out of a truck that I drove, and it was smooth over 50, and the truck that has the vibration now, didnt have it before. All I can do is check U-joints. It does clunk pretty loud going into gear.
     
  14. 76chevy

    76chevy 1/2 ton status

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    I have the same problem. Starts about 60-65mph. Vibrates on then off. The faster you go the faster it gets. (No nasty jokes please /forums/images/icons/wink.gif ).

    I've replace tranny mounts, engine mounts, 4 ujoints, a cv joint, and the thing still does it. At least the front drive shaft doesn't bind anymore.

    Today, I noticed my driveline is the same exact angle as my rear pinion. I believe this is wrong. The pinion should be within one degree of the rear output shaft of the transfercase.

    All this time and I never noticed it. Now I'm wondering if I put my taperred lift blocks in backwards and acidently shimmed the pinion up because it sure as heck isn't close to the other one.

    You might look for a problem like that. Maybe your yoke is bad like mentioned before. Fill it with grease and see if it the vibration disapears for a day or two. My yoke wiggles (transfercase and tranny in N) so I'm pretty sure it is worn too.
     
  15. mountainexplorer

    mountainexplorer 1/2 ton status

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    I did find something. The yoke on the back of the transfer case has play in it. I can grab the yoke and move it a little bit.
     
  16. or2play

    or2play 1/2 ton status

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    What your describing is almost the same thing I had in my truck. If the yoke on the driveline has play in it, that could be part or mabey all of the problem. What rear end are you running?
     
  17. testosterone

    testosterone Registered Member

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    my truck did the exact same thing...till one day the tranny blew....new tranny and no more vibrations. i kept thinking that my tires were out of balance or the tread was seperating. turned out to be the tranny...
    good luck with that
     
  18. mountainexplorer

    mountainexplorer 1/2 ton status

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    It's a 14 bolt rear end. The tranny is a TH350 with about 35,000 miles on a rebuild. Are there bearings around the tailshaft of the 203 T-case that wear out? That T-case yoke is definitely a bit loose. Driveline seems to be fine, and the slip yoke on the driveline is good.
     

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