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Driveline slack!

Discussion in '80-Series Tech' started by Seminole, Apr 9, 2003.

  1. Seminole

    Seminole

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    ???
    Finally made it over to this forum. Need some help/advice diagnosing the problem with the excessive slack in my drive line, specifically the rear. It's a 91 w/ 205k. Checked the u-joints-good, was just into the rear diff to change out the rear seals and wheel bearings and found no sign of excessive wear or play (no metal shavings, ring and pinion were in great shape, no leaks, clean diff fluid). With the truck level and in park, I can rotate the rear drive shaft about 3/4 of a turn before it catches. No side to side play in the shaft. No noticeable problems in the transmission (noises or shifting). Can anybody point me in the right direction? X-fer case? Tranny? or is ti the rear diff? I want to install an ARB in the rear but need to find out if it is a diff rebuild I am looking at or something more serious before I spend precious #6 funds on the locker. Thanks for any and all assistance.
     
  2. landtank

    landtank SILVER Star

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    My vote goes to the rear diff. I had gears installed about 6 months ago and can tell you that with the t-case in nuetral the shaft should only turn about 1/2". I placed a mark on the flange and then measured the difference it moved. I did this to evaluate how well the backlash was setup. If you do the same and you get 3/4 turn then it has to be in there.

    Rick
     
  3. yomama

    yomama

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    Seminole,

    I dont' think you have a problem there. I would be willing to bet that my 80 with 44k on it would probably do the same. I think it is normal, most vehicles can turn half a turn before things tighten up. Put the lockers on and don't sweat it till something really goes wrong....

    Yomama
     
  4. woody

    woody Internet Fireman Staff Member

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    3/4 turn as in 270 degrees?!?!? yikes...

    with the tranny in park, the rear shaft should barely turn at all. Additionally, with the rear tires on the ground, it should barely turn.

    Test the tranny output flange and the diff niput flange with the d-shaft removed and let us know, in estimated degrees, what amount of movement their is....a cheap plastic degree wheel might not be a bad idea either to provide an accurate number...

    I have a difficult time believing 270 degrees....that's a LOT of slop, and means major damage somewheres....
     
  5. Gumby

    Gumby Supamod Staff Member s-Moderator

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    3/4 inch I could do, but not 3/4 turn. Assuming the d-shaft is roughly 3 inches in diameter, you're saying the driveshaft is moving betwen 6 and 7 inches? By not catching, do you mean the driveshaft turns, but the rear wheels don't turn for 3/4 of a turn? that's gotta be in the diff and it is way excessive. My 80's not at the shop today or I would go out and look, but that seems WAY too much to me.
     
  6. Seminole

    Seminole

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    Thanks for the replies. I am an F'n idiot. I was distracted at work when I posted earlier. I meant to say I could rotate the DS about 3/4" to 1.5" (@10-15 degrees). I am also getting the "clunk" when shifting from P - D - R and when I let off the gas at speed. I was thinking the backlash in the rear diff originally? Do I need to rebuild or can the backlash be adjusted ? (still trying to make an excuse to buy the locker) Any help is appreciated.
     
  7. landtank

    landtank SILVER Star

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    As i stated earlier I marked the companion flange and measured the travel to be 1/2". This is with 4.88s. If you have the factory gears which I beleive are 4.10s then the travel should be even smaller for the same amount of backlash. I however am running a 96 and am not sure if it is completely compatable with yours. I would start by comparing the front to the rear. If you get a noticable difference between the two that might shed some light on the problem.

    Rick