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Slow speed driveline vibration

Discussion in '40- & 55-Series Tech' started by Anvil, Jul 6, 2011.

  1. Anvil

    Anvil SILVER Star

    I have searched the forum for a solution to no avail. If I missed it, please point me in the right direction.

    Here's the problem... Occasionally, when I come to a stop, the rear drive line make a horrendous sound, as if the drive line is in a bind. It only happens below 7 mph as I am decelerating. Other than coming to a stop, there is no vibration at all.

    A little history... I have a 74 40 with 2.5 OME lift, which sags in the rear a bit, (I have new Alcans on order) with extended shackles. I recently had a bad drive line vibration and actually lost a rear drive shaft due to incorrect angles. I now have the flanges shimmed within 2 degrees of each other, new u joints, no slop in the rear diff yoke, there is slop in the front diff yoke, which I plan on repairing soon.

    Any suggestions for a remedy? Any help would be appreciated!!!
    Thanks!
  2. 1bad40

    1bad40 Regular Member

    Messages:
    74
    Without riding in your rig I wouldn't be able to tell you what was wrong. Though there are alot of guys here that know alot more than I do, I want you to rule out another possibly, not likely, but possible. Are your tires worn like a saw blade with high and low spots? I had a set of Cooper Discoverers on my '95 Silverado that wore like that and it would shake the pi$$ out of my truck coming to a stop. Didn't do anything at speed, only, like you said, 7 MPH or less. I don't know if that's an IFS issue or if it happens with all 4 bys but check it out.

    My long distance provider is Black Hills Ammunition.
  3. Anvil

    Anvil SILVER Star

    Thanks for the input! Thats interesting...I running ProComp MT's 33 x 12.50's with less than 3000 miles on them and they look fine. I'm still at a loss... Thanks!
  4. Brian in Oregon

    Brian in Oregon New Member

    Messages:
    3,042
    Pull the drive line and take out the u-joints, and inspect them with the needle caps off.

    My son had a similar problem on his Bronco. Drove fine but problems. We kept looking for problems but did not pull the driveline. Should have, it was binding at slow speed but appeared to be good at higher speeds. I always assumed that any slow speed problem would be magnified at speed, but apparently that is not universally true. The u-joint finally grenaded while he was driving in slow traffic.
  5. Toshi38

    Toshi38 New Member

    Messages:
    1,979
    Location:
    Malmö, Sweden
    check how much your pinion angle changes on deceleration... you could be creating binding when the diff moves due to the deceleration/braking ?
  6. Degnol

    Degnol SILVER Star

    Messages:
    8,123
    Location:
    Kansastitty
    Inadequate spline engagement can cause vibrations that come and go.
  7. Anvil

    Anvil SILVER Star

    Thanks guys, I'll check the ujoints tonight.

    When I come to a stop, it sounds as if the u joint is binding...

    Toshi38... How do you check the deceleration angle?

    Degnol.... Inadequate spline engagement? The new drive shaft is a VERY tight fit. Could this be the problem?
  8. Degnol

    Degnol SILVER Star

    Messages:
    8,123
    Location:
    Kansastitty
    When I grease the splines, I pump it full, then remove the zerk and drive around a little then put it back in. you can add too much grease that has no way out, pretty much negating the splines and their intended slip.

    With your lift, there can be too little engagement of the splines. It will still feel tight, but can vibrate like hell either accelerating or decelerating.
  9. Toshi38

    Toshi38 New Member

    Messages:
    1,979
    Location:
    Malmö, Sweden
    Easiest way would be to get a friend to watch you decelerate... I don't know much about the topic....

  10. Degnol

    Degnol SILVER Star

    Messages:
    8,123
    Location:
    Kansastitty
  11. Anvil

    Anvil SILVER Star

    Thanks again guys!

    Degnol... I read the thread you provided. Thank you! I learned a bit.

    My drive shaft is a VERY tight fit. I actually had to shave off 3/16 of an inch of the yoke and spline in order to make it fit. Is it possible the drive shaft is too tight and has no play? Again, the problem is occasional, I'm guessing it occurs 40 maybe 50 percent of the time.

    I truly appreciate everyone's input! :cheers:

  12. Cdaniel

    Cdaniel Undocumented Mechanic SILVER Star

    Messages:
    2,378
    Location:
    AZ
    I'm curious as to how you have "shimmed" the flanges to within 2 degrees of each other. Any pics?
  13. Cruizerjunkee

    Cruizerjunkee Regular Member

    Messages:
    96
    I did this on my 62, u-joint gave out as a result.
  14. Anvil

    Anvil SILVER Star

    Good question. I used an angle finder to find the difference in angles. I then milled the wedges (5 degrees) from some aluminum I had laying around and installed them under the spring plates. No pics, but I can get some if necessary. Thanks!.
  15. Cdaniel

    Cdaniel Undocumented Mechanic SILVER Star

    Messages:
    2,378
    Location:
    AZ
    Ahh good then. I got the idea you had added some sort of shim to the actual flanges.
  16. Toshi38

    Toshi38 New Member

    Messages:
    1,979
    Location:
    Malmö, Sweden
    This could be your issue right here... when you decelerate I believe the drive shaft gets a little shorter (from the pinion moving) which could posibly result in binding if its too long?

    I know I had the opposite problem under acceleration (only a tiny bit of splines contacting) ... but like I said I don't know a ton about it so I could have it backwards...
  17. Anvil

    Anvil SILVER Star

    Toshi38... I'm beginning to agree. I have double checked all the other possible culprits.:bang:

    Before I shave off another 3/16... Has anyone else had this problem?
  18. 3_puppies

    3_puppies SILVER Star

    Messages:
    6,964
    Location:
    Helena MT
    Wayne, with your lift and otherwise stock configuration. That driveshaft should have plenty of room. If it's tight, that's bad and has no compression left in it and can actually damage the transfercase. There should be movement both ways in the driveshaft slip joint.
    I'll get a measurement on mine tonight, transfer to axle, but maybe someone else can post up the measurement.
    Paul
  19. Anvil

    Anvil SILVER Star

    Thanks Paul! I appreciate the help. I'll measure mine again as well. Also, thanks again for the drive shaft.:clap: I hope to make it over to Helena and visit your "warehouse" one day soon...

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