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Need driveshaft help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by '73 K5, Oct 18, 2000.

  1. '73 K5

    '73 K5 1/2 ton status

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    After I put my 2.5 inch lift on in the front of my Blazer, the driveshaft had pulled apart quite a bit at the slip yoke. So I took it to a driveline shop and had them lengthen it 1.5 inches. Now it almost looks too long when I put it back in today. Maybe not, but I figured I should ask before I damage something. At rest on a level surface, the driveshaft has about 1 or 1.5 inches to compress before its all the way together. Is that enough for mild 'wheeling or am I going to bottom it out??? Help

    '73 K5
    Chevy good...Ford bad
     
  2. '73 K5

    '73 K5 1/2 ton status

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    Come on guys, its been over 6 hours since I posted this. Someone out there has to be able to help me. Please

    '73 K5
    Chevy good...Ford bad
     
  3. UseYourBlinker

    UseYourBlinker 1 ton status

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    I had the same problem I installed a 2.5 inch lift and kept on throwing out U-joints.I went to my buddies work (driveline shop)and they told me that the driveline was about a 1 1/4 to short. Anyways I bought a new driveshaft installed it and never had another problem! (knock on wood)hope this kinda helps
     
  4. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    Klunky!! Sup dude?? How ya been man?? Hmmmmm driveshaft huh?? Haven't thought about one of those in long time. I'm sorry I'm not helping you out on your post here. Did you ever put your top back on your truck?? Damn dude, I need to stop by and see you one of these days. Do you want me to stop by with or without the drunken friend?? HAHA I still got your pager #, so maybe I'll just have to page you after I buy another tire for the 'Vette'. Then I'll come see ya. Peace man.

    Alex
    [​IMG]What me get stuck? NEVER!![​IMG]
     
  5. Panther

    Panther 1/2 ton status

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    Sorry I'm not answering your question either but which driveshaft are you talking about (front and/or back). I wanna do a 2.5" lift and am trying to figure out all the extras. Thanks.

    <font color=blue>I don't get stuck, I'm just in the mud when I stop for lunch [​IMG]
    - NJFourWheelers</font color=blue>
     
  6. Blue85

    Blue85 Troll Premium Member

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    Now, maybe I'm looking at this wrong, but a 2.5" lift will not make the static length of the driveshaft more than about 1/2 inch longer. If 1 1/4" was the length that you needed, then the driveshaft was too short stock.

    It's pretty easy to estimate the change in length just using Pythagorean's theorem (any painful flashbacks to basic high school geometry?) I'm not sure what the length of the shaft is stock, but I'm guessing that it's about 30". The square root of 30 squared plus 2.5 squared is only 30.1". This is based on the assumption that the driveshaft is basically flat when the truck is stock, which is pretty close to being accurate if my memory serves correctly. If you need to add half of the length of the lift to the driveshaft, that implies that the driveshaft is at 45 degrees.

    To figure things out more accurately, you would need to get under the truck and measure lengths and angles and then just work through a little more complicated geometry.

    To me, it seems more likely to chuck U-joints based on bad pinion angles after a small lift then because of driveshaft length. The exception to this would be if you are wheeling and dropping the axle to full droop a lot and limiting the droop by fully extending the slip joint in the shaft. Is that the case?

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  7. BLzr4x4ngkid

    BLzr4x4ngkid 1/2 ton status

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    "Don't hit me with those negative waves so early in the morning." Odd Ball from the movie Kelly's Hereos.

    Ahhhh the love math. I used to dig doing stuff like that. I'm glad you mentioned that theorum, because I never thought about using that one. Good call man.

    Alex
    [​IMG]What me get stuck? NEVER!![​IMG]
     

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