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Driveshaft ???

Discussion in 'Ford Trucks' started by HALH VT, Dec 13, 2008.

  1. HALH VT

    HALH VT Senior Member
    from Vermont
    Messages: 128

    My '79 Ford F150 sat in an unheated garage for most of the last ten years before I got it in 2001. I have had multiple corrosion/deterioration issues because of that.

    Three years ago the splines on the rear drive shaft stripped. I cut the end out in my lathe and replaced it with one from another shaft. At the time I had half a thought that maybe the tube should be replaced as well, because it had deep rust pitting.

    Fast forward to yesterday afternoon, when it stopped going forward with a bang. A crack starting where the weld burned through one of the rust pits suddenly opened up and the whole shaft end laid on the ground.

    So the question is:

    I have it re-tubed, and I am not sure about the phasing of the U-joints. It has a single joint on the splined end, which is next to the rear axle. The end at the T-case is a double cardan? joint, like you more often see in a front drive shaft. Do you line the yokes up as if they were both single joints, or do you split it 45 degrees as you do in some three joint shafts. I have it installed now in the aligned position. I plowed for three hours last night after it was repaired, and didn't fell any vibration. This truck doesn't get much over the road use, mostly local and around the farm, so maybe it doesn't make that much difference.
     
  2. Spitz

    Spitz Senior Member
    Messages: 192

    The joints should be in phase together (Both caps in the same direction). Although if your off you may not feel it driving at slower speeds with the double cardan, its a constant velocity joint..
     
    Last edited: Dec 13, 2008
  3. HALH VT

    HALH VT Senior Member
    from Vermont
    Messages: 128

    I don't really understand the layout of this drive train. Most older 4x4's I have seen use one single joint and one constant velocity joint in the front drive shaft, coupled with single joints in the front axles. This makes the whole front drive more or less constant velocity, depending on the steering angle. The rear drives use a single joint at each end of the drive shaft for the same effect. This truck, 1979 F150 short box, uses just the opposite. A friend who was a Ford dealership mechanic says he thinks the extra joint in the rear shaft is to accommodate the extreme drive shaft angle at the transfer case. The long boxes and the F250's were set up the other way.

    As I said in my previous post it probably doesn't matter that much, as it won't be running over the road for long distances, and it must have worked fairly well when these trucks were shiny and new.
     
  4. Spitz

    Spitz Senior Member
    Messages: 192

    I think they are for the extreme angles as well.. I know they use the quite often in lifted vehicles.. Each joint takes half the angle instead of the full angle a single one would. If you look at your pinion angle it should be pretty close inline with the driveshaft angle, its suppose to be close. My guess is the "wind up" is decreased and less vibration at speed..