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'63 Hawk Drive Shaft Orientation

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  • Drive Shaft: '63 Hawk Drive Shaft Orientation

    My driveshaft has run-out of .022" to .026" at the trans. end w/ only .005 to .007" at the diff end w/ .012 to .015" at the mid-point. Can the driveshaft be swapped end-for-end or is there a difference between the ends (other than the U-Joints) that might be a problem? Swapping end to end would (hopefully) isolate the run-out problem to the drive shaft or to the splined yoke.

    Anyone have any ideas re; the swap of ends?

    Appreciate any help .

    Paul TK

  • #2
    A driveshaft can run left or right or up or down but not both. If you are concerned about it being on center perhaps you can adjust the rear motor mounts for alignment. It is also imperative that the bearing cups are pressed all the way in. It might be a good idea to take it to a drive line shop and have it confirmed. Usually the balance weights are at the rear portion of the shaft therefore it may not be a good idea to swap ends, however check with a driveline shop.

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    • #3
      Do you actually have a driveline vibration? What is the midpoint run out if you flip the rear u-joint 180 degrees. It's already close to being "right on" for a mass produced driveshaft in the center. Check the trans end u-joint is actually centered correctly, that might be all you need to get it right.

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      • #4
        What is the cause of the "run-out"? Perhaps you have a bent driveshaft or U-joint crosses/bearing caps not properly centered/aligned.
        Other than a different driveshaft, I think a check by a good driveshaft shop is key to the solution of your "problem". I put problem in quotes becuse I do not know what the problem is, perhaps vibration or concern of wear.
        Gary L.
        Wappinger, NY

        SDC member since 1968
        Studebaker enthusiast much longer

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        • #5
          The drive shaft was vibrating prior to R & R'ing the engine and trans. The check for run-out was made both for the prior vibration problem and just because it was another check on the installation (I always check whatever possible before running into a problem - It has paid off in the past).

          Thanks for the leads, I'll check the front U-joint install first, then off to a drive shaft shop (two in the area).

          Re; balancing: for what shaft RPM should the 'shaft be balanced? (one shop that has been very reliable specializes in truck work, and balances to 2,500 - 3,ooo 'shaft RPM; The other shop I have not used - They balance to whatever is requested (the higher the RPM, the higher the cost). As long as the 'shaft is set up for alignment it is not much more cost to check the balance.

          Thanks again,

          Paul TK
          Last edited by Paul Keller; 05-31-2016, 11:38 AM.

          Comment


          • #6
            Originally posted by Paul Keller View Post
            The drive shaft was vibrating prior to R & R'ing the engine and trans. The check for run-out was made both for the prior vibration problem and just because it was another check on the installation (I always check whatever possible before running into a problem - It has paid off in the past).

            Thanks for the leads, I'll check the front U-joint install first, then off to a drive shaft shop (two in the area).

            Re; balancing: for what shaft RPM should the 'shaft be balanced? (one shop that has been very reliable specializes in truck work, and balances to 2,500 - 3,ooo 'shaft RPM; The other shop I have not used - They balance to whatever is requested (the higher the RPM, the higher the cost). As long as the 'shaft is set up for alignment it is not much more cost to check the balance.

            Thanks again,

            Paul TK
            Since I doubt that in every day use you will be driving at 5000 RPM in top gear, I would guess a good balance at 2500 (1/2 speed) would be good enough and probably be close to where it would be at 50 MPH or so. Since you are reinstalling the trans and engine-be sure to replace the front and rear motor mounts if you haven't already, you didn't mention if it's manual or A/T.

            Comment


            • #7
              Are there any balance weights on the driveshaft?

              I'd mark the "high spots" at the ends and the middle to look for a problem.

              If the front yoke has a machining problem with centering, then a "perfect" driveshaft's runout at the trans and middle will have "high spots" close to inline.
              I saw an OEM driveshaft from a Dodge van (it could have been any make) that caused the front to have runout of about 0.06". Picture one snap ring groove being at a short radius and the opposite snap ring grooves at a larger radius, so the u-joint and driveshaft would be moved off center.

              The factory had balanced the assembled driveshaft to compensate.
              The owner had not marked things as they came apart, so he assembled it so the former driveshaft high spot was now the low spot, and the whopping balance weight (attached at the former low spot) was now on the high spot, doubling the error.
              The first drive revealed a problem, so he brought the shaft to us for balancing.
              We could have stripped off the weight and put a big weight opposite, but simply flipping the driveshaft in the yoke removed about 95% of the imbalance.

              Comment


              • #8
                You can also heat a driveshaft, and quench it with a wet rag to shrink the high side back straight!
                Bez Auto Alchemy
                573-318-8948
                http://bezautoalchemy.com


                "Don't believe every internet quote" Abe Lincoln

                Comment


                • #9
                  I have a question regarding drive shafts, and it probably applies to any spinning item requiring true concentric accuracy. On a drive shaft, should it not be "trued" before it can be balanced? I can see that balance must be to ensure that centrifugal forces, at speed, are equally applied. Are truing and balancing two separate operations?

                  However, if the shaft is not perfectly centered (true)...will it really balance? In other words, can a shaft with a real physical eccentric run-out, ever operate smoothly, even if balanced? If so, my thinking is that there is a very tight tolerance in which this can occur, and very little wiggle room for the slightest wear in bearings.
                  John Clary
                  Greer, SC

                  SDC member since 1975

                  Comment


                  • #10
                    Old school driveline shops with older equipment balance at lower rpm's.
                    Newer shops balance at much higher rpms.
                    I would ask a shop how new their equipment is.
                    The charging per rpm of balance is bogus.
                    Balance the unit as a whole.

                    Also, you can't swap your tube end for end because of the previous balancing.



                    Originally posted by Paul Keller View Post
                    The drive shaft was vibrating prior to R & R'ing the engine and trans. The check for run-out was made both for the prior vibration problem and just because it was another check on the installation (I always check whatever possible before running into a problem - It has paid off in the past).

                    Thanks for the leads, I'll check the front U-joint install first, then off to a drive shaft shop (two in the area).

                    Re; balancing: for what shaft RPM should the 'shaft be balanced? (one shop that has been very reliable specializes in truck work, and balances to 2,500 - 3,ooo 'shaft RPM; The other shop I have not used - They balance to whatever is requested (the higher the RPM, the higher the cost). As long as the 'shaft is set up for alignment it is not much more cost to check the balance.

                    Thanks again,

                    Paul TK
                    HTIH (Hope The Info Helps)

                    Jeff


                    Get your facts first, and then you can distort them as much as you please. Mark Twain



                    Note: SDC# 070190 (and earlier...)

                    Comment


                    • #11
                      Well we'll see what happens, but my guess is the driveshaft guys will install 2 new u-joints and the problem disappears. Over thinking the problem-- it's less than 1/64th inch out. Or the engine mounts or trans mounts were broken , or an aftermarket exhaust was vibrating in resonance.

                      Comment


                      • #12
                        Unbalance has inch ounces (or gram cm) as unit of measure. IE, a weight times a distance from centre of rotation.
                        The rpm has nothing to do with unbalance, the unbalance is always there regardless of rpm's.
                        However, the EFFECT of unbalance is felt stronger at certain rpm's.
                        The rpm's for balancing depends on the balancing machine, ie different machines are designed to operate at different rpm's.

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