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Pinion Angle

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by i_4x4, Dec 10, 2000.

  1. i_4x4

    i_4x4 1/2 ton status

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    A buddy & I looked a K5 that he was intrested in purchasing. But when out on the test drive we felt a vibration on decell. When we got out to look the angle of the pinion was about paralell w/ the ground & drive shaft looked about 10 to 12 degrees, while at the t-case it looked about 4 to 5 degrees. This Blazer has a 2in. lift suspension, 14 ff. Any ideas? Other than that it seems to be a good deal.

    Thanks i_4x4

    LET'S ROCK
    Don't follow me you will get STUCK!!
     
  2. fr8train

    fr8train 1/2 ton status

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    Thats kinda tricky. In my own experience it should vibrate upon exceleration too. The angle of the pinion should be a little lighter too. Was this vibration with the brake pedal applied or when you were coasting?
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Thats a pretty minor thing, just shim the rear end until you have the correct pinion angle. You could use it as a bargaining point though.

    Rene

    [​IMG]
     
  4. i_4x4

    i_4x4 1/2 ton status

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    Only under coasting conditions. Sorry for not mentioning it earlier. Thanks again.


    LET'S ROCK
    Don't follow me you will get STUCK!!
     
  5. Hobbes68

    Hobbes68 Registered Member

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    Are the u joints tight? Sounds like they may be a bit worn.
     
  6. fr8train

    fr8train 1/2 ton status

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    Also could you tell wether vibration was coming from the front, back, middle, or one side in particular? Ok U-joints may be to blame, but it would vibrate on accel too. Just in case wiggle both drive shafts to see if there is any play. Rule that out and then look at the wheels, any weights missing, rim irregularities, or loose lugs/missing lugs? Also if it was lifted recently are any of the bolts on any of the springs, u-bolts, steering, shocks, AND u-joint straps/u-bolts loose?
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    the angle at the case should be within a couple degrees of the rear. The reason you feel it on decell and not accell is under load the pinion will come up but on decell it will drop. My bet is the rear lift is blocks and your getting excessive wrap as a result. Should be easily cured. Best thing to do is loose the blocks and if possible do a shackle flip and lift spring. It took 5 degrees rotation to get my angle correct and thats more then you really want to do with a shim. If I bought the truck I would cut the spring purches and rotate and reweld for the best results. I'm on a 4 inch lift with a 2.5 deg shim in the front and running full time and NO vibes all the way up to 75mph. Never had to replace the u-joints and if your angles are correct you shouldn't Now with a CV or carrigan joint drive shaft you should have zero andle at the pinon and the CV should have all the bend. The problem is the more the lift the more you rotate the front axle the worse Caster angle you get the more difficult it is to correct.
    I would use this as a brgining tool and qute some rear spring prices. Would be about $350-400.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     
  8. Derf00

    Derf00 1/2 ton status

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    After my 4" lift, I had this very same problem, vibration upon deceleration. Since the drive shafts were a little on the short side, I had them lengthended, that did not help. Lowereing the transfer case solved the problem. I used tapered blocks in the rear when I did the lift.
     

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