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  • Frame / Springs: Shimmy-lurch

    56 Power Hawk, 259, 3 spd manual, OD:
    Just today I noticed that when I lift off the gas my car lurches to the left. When I give it some throttle, it lurches to the right. The feeling is like driving a van and getting hit with a side gust of wind. Its most noticeable at highway speeds, but also does it in 2nd gear/2000rpm speeds. Its very disconcerting. It feels like its coming from the back, as if the rear axle is somehow loose.
    I did a check under the car today, couldn't see anything out of the ordinary with shocks, axle, spring mounts & shackles. Front suspension looks OK.
    The last stuupid thing I did that might be relevant; I did a quick start in 1st gear, squealed the tires... but It was in overdrive 1st. (previous owner modified OD so it stays in OD unless I flip a toggle and pul out handle).
    Could I have messed up a motor or trans mount? Any ideas?

  • #2
    Is this the same car that you put wider wheels and tires on the front, than the rear?

    BTW, a hard launch in First OD is a good way to blow apart your transmission. The OD planetary can’t withstand that kind of torque.


    • #3
      Yes, after lowering car back to stockish height, 235/70/15 rubbed on fenders, so I put them on front and then put 205/75/15 on rear. That was a week or so ago. See attached image.
      Good to know about OD planetary, it sure felt wrong when I did it. At the time I was worried that I damaged something, but then drove another hundred miles without incident.
      Attached Files


      • #4
        Spend the time to get the OD back to how Borg-Warner wanted it to operate. You and the car will be much happier.

        Look well beyond the Studebaker suppliers in your searches. Willys, Nash, Packard, Mercury/Ford all used very similar electrics as we did. The relay change in 1955-1956 for all marques was key as it was also around the change from 6V to 12V, which also might have changed the polarity.

        Fifth Avenue Internet Garage and Vintage Auto are two well-known suppliers for B-W R10 and R11 systems as well. Even odd sites like “Herm the Overdrive Guy” have been terrific info sources:


        • #5
          I have a question about the lurching. Do you also experience pulling (hard or otherwise) when you apply the brakes hard? If so, it could be an indication that your Bell Crank is worn out and needs to be replaced.
          Ed Sallia
          Dundee, OR

          Sol Lucet Omnibus


          • #6
            That "shimmy-lurch" is called "torque steer". You might have a broken center bolt in a rear spring. And you should fix the overdrive, and put it back to factory specs.
            Gord Richmond, within Weasel range of the Alberta Badlands


            • #7
              Thanks Commander Eddie, the brakes work quite well, no pulling when stopping hard. The bell crank is the center steering linkage part, right? I will check that. This lurch happens at very gentle throttle settings, just cruising at 60, let off gas to slow to 55, gently get on gas to get back to 60. It just does it initially, not the whole time I accelerate or decelerate. There is minimal steering correction to compensate. But it feels unnerving.
              Gordr, I will check my center bolts in rear springs. Thats what it feels like, like the axle is shifting around.
              Awhile back I posted about my particular OD set up. I got a bit lost in the details, explanations, and advice... and have so much else more pressing to fix (seats, jacked up rear, door windows, rust, exhaust...) I'm very good with motorcycles, but this is my 1st old car, so it can be a bit overwhelming. Perhaps its time to revisit the subject.
              NCdave51, I will check out your recommended sources.


              • #8
                Originally posted by Rafe Hollister View Post
                56 Power Hawk, 259, 3 spd manual, OD:/Cut/I did a quick start in 1st gear, squealed the tires... but It was in overdrive 1st. (previous owner modified OD so it stays in OD unless I flip a toggle and pul out handle).
                Could I have messed up a motor or trans mount? Any ideas?Thanks,Rafe
                I am guessing that you lifted the Gas after the Hard Start and it would have shifted to 1st. Overdrive with a BANG, correct?
                This could definitely damage the Overdrive Planetary Unit and other Parts.

                I am trying to relate that O.D. Damage to your Lurching Left and Right with Accelerating or Decelerating, so not sure if that would be the cause.
                Second Generation Stude Driver,
                Proud '54 Starliner Owner


                • #9
                  Gordr had it closest. When I lowered it back to stock, I put on new U-bolts. The box says to re-torq them after a few hundred miles. I should learn to read directions first . The right side axle was moving around a bit on the springs.
                  My OD luckily seems to be fine. StudeRich, the previous owner made it so once its in OD, it stays there. So until I come to a complete stop and shift it out, I have 1st, 2nd, 3rd all in a higher range, and reverse doesn't work.


                  • #10
                    you should be able to simply turn off the switch and it will come out after lifting your foot from the gas. You should really go back to factory wiring, and you may in fact have a mechanical problem with that unit.

                    try this: get the car up to about 45 the way you normally drive it (overdrive on), turn off the switch, let up on the accelerator, hit the clutch and just gently tap the brake.

                    Does it come out then? you will know when the engine speeds up noticeably from what it was before, upon reapplying the accelerator.

                    if that works, try eliminating the clutch part of the the above, then the brake part of the procedure.

                    Realistically, you just need to let off the gas a moment and it should engage or disengage. basically you are taking the torque off and allowing the pawl to move.

                    if you can get it to work by simply letting off the gas for a second, sometimes reapplying and letting off again helps, then you may not have a mechanical problem. However, like I said, best be to return to factory wiring.


                    • #11
                      Check your leaf spring bushings, and also the rear frame shackle bushings. I had a 63 GT years ago that they were totally shot, and had the same symptoms you describe. After they were replaced, it handled like a new car....totally different.
                      Bez Auto Alchemy

                      "Don't believe every internet quote" Abe Lincoln


                      • #12
                        Thanks Corbensteino. But right now my car so many more pressing things to fix (had it 2 months). For me, I have to be able to conceptualize how things work, and if I can't, I just get confused. MY OD works fine for me and long as I don't do drag race starts. So for now, putting it back to stock is low priority.


                        • #13
                          I believe the reason this Overdrive never goes back into Direct, is the FO disconnected (Bi-passed) the Governor.

                          The Manual Switch Kickdown Switch Conversion you have will work properly if you re-connect the Governor.
                          It has No idea whether or not you have reached the Upshift Point (Speed), or Downshift Point.
                          Second Generation Stude Driver,
                          Proud '54 Starliner Owner


                          • #14
                            I believe I may have a similar situation as Rafe with the overdrive. I have a stripped down OD - no kick down switch - just my OD cable and my off and on switch. The switch activates the solenoid which puts it in OD and locks out reverse. The cable locks out reverse when pushed in for OD. So - the on/off switch has to be off and the cable pulled out to get into reverse. The system is real cool once you get the hang of it. The trans is a modified M5 floor shift by Jerry Kurtz - really nice. I drive with the cable in OD most of the time and the switch off until I need OD - I drive a lot in 2nd and 3rd OD. @55mph I’m tacking about 1,900. Click image for larger version

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                            • #15
                              Wow, thanks Rowan. Sounds like same system. From what you said, it sounds like I can leave the cable in OD all the time, unless I need reverse? Is that correct?
                              What is a M5 floor shift? Mine has been converted to 3 on floor with shifter coming straight outa top of trans. Nice looking truck.
                              In regular 3rd I'm taching 3,000 at 70mph. In OD it drops to 2,000. I have 3.73 diff.