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'65 Daytona, Pinion Angle "Broken Back" configuration???

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  • Drive Shaft: '65 Daytona, Pinion Angle "Broken Back" configuration???

    '65 Daytona (automatic), single drive shaft:

    As best my eyes can tell the angle of my transmission AND my differential both angle downward. From what I was able to find on the Internet (very limited) this is referred to as a "Broken Back" driveshaft configuration. Is this typical for this year/model Studebaker?

    99% of what is on the Internet deals with the "parallel output shaft/parallel pinion shaft, equal opposing angles." Any input would be appreciated.

    Thanks, Tom
    '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.

  • #2
    Your crankshaft (trans yoke) 'plane' and your pinion 'plane' should be equal at ride height.
    Whatever the u-joint angle is up front (the angle of the yoke as compared to the angle of the driveshaft) needs to be the opposite at the rear.
    If you have a 3 degree angle 'down' at the front, you should have a 3 degree angle 'up' at the rear.
    Some drag racers put the pinion angle 'down' a few extra degree's knowing that under hard acceleration the pinion will 'climb' the ring gear and, due to spring wrap', the pinion will rise.
    But that's racer stuff and it makes deceleration vibration on street cars.

    Keeping the pinion shaft and crankshaft in 'plane' is important for u-joint life, as you need some rotation of the bearings in the cups to prevent 'brinelling' and shorten your u-joint life.
    There is also the same rule on side to side. Stude shifted the engine over to the RHS for steering gear clearance.
    But the same rule about 'planes' still applies.

    It's just one of those 'tuning' things you need to do to get the best ride, performance, and parts life....
    It's good to know.
    HTIH (Hope The Info Helps)


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

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


    • #3
      Wittsend, what you observed is the way Studebaker built them - right or wrong. Also if you remove the driveshaft, and eyeball the universal joints, you will find that they are out of phase by some 11-13 degrees, as I recall. Apparently they had their reasons for that setup.


      • #4
        Check the leaf spring bushings and the transmission mounts. If these are worn out, you'd be 'down' up to an inch at the trans and 'up' a half inch at the diff.........

        Also the front leaf bolts have certain holes they use. Are they in the right holes?


        • #5
          Revised question 6-2-12

          "Also if you remove the driveshaft, and eyeball the universal joints, you will find that they are out of phase by some 11-13 degrees, as I recall."

          OK..., so..., what should I do? I already have a driveshaft that fits properly lengthwise (from a '76 Buick Skylark). But, it doesn't have this phase offset (which, yes, I did see when sighting down the original Studebaker shaft).

          Should I follow "standard" (but non-Studebaker) procedures and parallel the output shaft with the differential pinion using the common valued + /- angles?

          If so, the engine tips back quite a bit and it would seem practical to raise the transmission as much as possible so as to not have an unreasonably high pinion angle.

          Also, as "S" stated there are other mounting holes for the leaf springs. It seems that the holes just above the position currently in use would be advantageous to inclining the pinion in the right direction and thus the need to use minimal wedges to get the proper angle.

          Any input would be appreciated.

          Thanks, Tom
          '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


          • #6
            Hi Tom.
            I went through the same thing with my Hawk. I thought that the leaf springs had gone "s" shaped and caused the tailshaft angles to go "broken back"
            The angles were 5deg on the transmission and 1 degree on the diff. (I had bad shaft vibration at 60 mph)
            After invesigation the springs were fine so I thought of caster wedges under the diff mounts. It just wont work. The transmission even with shims points down abut 4 deg. and 3deg down on the diff. To get them parallel you have to rotate the diff up 7deg. Then you end up with about 6deg equal at both ends which is far too much for good unijoint life.
            I then decided that Studebaker must have designed the Hawk driveline to be broken back. It is unusual today but it does work.
            I then simply shimmed the rear engine mounts to give the correct angles.
            Ended up with about 3 deg front and 3.5 deg rear. Alowing a bit for diff wind up at 60mph and above. The angles should be equal at speed. about 2.5deg.
            It took a lot of measuring but it is now smooth as silk.
            Its just how Studebaker made them.
            Allan Tyler Melbourne Australia


            • #7
              [QUOTE=wittsend;651116]"Also if you remove the driveshaft, and eyeball the universal joints, you will find that they are out of phase by some 11-13 degrees, as I recall."

              OK..., so..., what should I do? I already have a driveshaft that fits properly lengthwise (from a '76 Buick Skylark).

              Why would you be using a Buick shaft? there is a lot of the right ones out there and easy to find.
              Castro Valley,


              • #8
                Tom...I'm thinking your stressing too much here. You've modified your car, and need to be prepared to trouble shoot, but try it out first. It seems like you've done your homework already in selecting the shaft. I would suggest you take the Buick shaft, install new u-joints, and have a shop check for staightness and balance. Once you know the shaft and joints are good, then install it and run the car to see what you're dealing with. Hopefully the car will be fine, if not...then start trouble least you know now that the shaft is not the problem, and you can concentrate on the geometry aspects. I am assuming the motor mounts are sound, and you installed a new trans mount on the GM trans? Good luck, hope it works well. Junior.
                1954 C5 Hamilton car.


                • #9
                  Allan: Thanks for the "been there, done that" information. Is 3 up/ 3 down really too much? That seems to be in the "ball park" of what I have been reading. This is a "hobby" car that I'll likely drive 500-1,000 miles a year. My concern with staying with the "broken back" configuration is the Buick driveshaft doesn't have the offset on the U-joints.

                  C&B Studebakers: The reason I'm using the Buick driveshaft is because the 700R4 transmission I installed is 3-1/4" shorter than the B-W transmission I replaced. At the correct length, correct yoke, a 1310 rear U-joint, and $20 out the door at Pick A Part, the Buick shaft it is a whole lot cheaper than having the original shaft lengthened.

                  Junior: Your probably right about seeing where it is at before I get too deep into correcting things. I just hate knowing I might have a problem and try and take care of things beforehand. Sadly my car needs a windshield and until I find one reasonably priced (and somewhat local) I have nothing to do but tinker.

                  Thanks to all, Tom
                  Last edited by wittsend; 06-03-2012, 05:28 PM.
                  '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


                  • #10
                    Hi Tom
                    What you end up with (on a Hawk anyhow) to remove the broken back is 6deg front and 6deg rear. I think that is too much to get long life from the uni joints.
                    I am running a Nissan 4n71b transmission and had to lengthen the tail shaft about 35mm. It’s a long story but you cannot lengthen a tail shaft. You have to have a one piece tube.
                    I supplied the maker the Stude diff yolk and the transmission yolk and he made the shaft. I forgot all about the offset so I don't think it has any offset. I will check next time I am under it.
                    The broken back works fine, you just have to be fussy setting up the angles allowing a little bit more on the diff to allow for diff wind up at speed.
                    As I said my hawk is as smooth as silk. Well the tail shaft is if nothing else.
                    The disadvantage of the broken back is that the angles vary front to rear with suspension travel.
                    Using the conventional setup the angles are always the same although they increase with suspension travel.
                    As you already have the tail shaft I would assemble it paying attention to the angles and see what happens. If it is vibration free (which it will be if the angles are right) you’re a winner.
                    Don’t throw money at something until you prove it does not work.
                    Sarcasm in the next sentence
                    This is the correct CASO principle. (CASH AWARE STUDEBAKER OWNER).
                    Allan Tyler Melbourne Australia


                    • #11
                      Ok, I'm B-A-C-K.

                      I leveled the car so I would have relevant numbers (front to back). I selected the mid point between the two doors and set the angle gauge on the frame rail. I jacked the car (at the differential) until the gauge read "0".

                      I got the following readings:

                      1. When I place the gauge on the differential yoke (vertically oriented) I got 2 degrees down. I confirmed this by rotating the yoke 180 degrees and re-measuring.

                      2. When I placed the gauge on the tail shaft I got 8 degrees down! This was confirmed at the output shaft, the seal area of the tail shaft and a perpendicular area on the cylinder head.

                      As I understand it (correct me if I'm wrong) my engine/transmission should point down 6 degrees and following the "rules" of driveshaft angles (and a "broken back" in particular) the differential should also point 6 degrees down.

                      The only way to get the tailshaft nearer to 6 degrees is to raise it up. Doing the math .9 inches is equal to 1 degree. And that is about all the room I have before tunnel clearance becomes an issue. So, at best I'm likely only to get the tailshaft no closer than 7 degrees down. Prior to installation I hammered out the tunnel in anticipation of clearance issues. So, I can't do any more there. And, yes, I do have new motor and transmission mounts installed.

                      On the differential side 4 degrees seems like a lot of wedge to add under the axle mount. BTW, I have checked the mounting holes and the hole that is selected is the one that already gives the most downward inclination. So, the axle can't be misplaced. I also checked the spring bushings,loaded and unloaded. There is minimal change and I doubt it even alters the reading 1/4 degree.

                      I think it is now obvious why I made my post. Visually things looked wrong and now with accurate measurements it is verified. A tailshaft that is 2 degrees too far down and a differential that is 4 degrees too far up just isn't right (for a "broken back" configuration). Yes, I changed the transmission, but the location of the tailshaft centerline is within 1/8" of the original B-W transmission. I've seen pictures of other Chevy powered '65-'66 Studebaker's (Lark type) and the engines ALL look like they tilt rearward significantly. Any thoughts???

                      Thanks, Tom
                      Last edited by wittsend; 06-06-2012, 09:26 AM.
                      '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


                      • #12
                        First off, don't worry about the level of the frame. The shop manual recommends that you measure the engine inclination on the bottom of the starter. The rear axle should be measured on the vertical face of the axle housing beside the pinion seal. You should also measure the inclination of the driveshaft. You will probably find that you have +6 degrees at the engine, +2 agrees on the drive shaft and -2 agrees at the rear axle housing. Thus adjusting for 0 agrees on the drive shaft (mathematically), you end up with +4 degrees engine, 0 drive shaft, and -4 degrees axle. The manual recommends that you have 1/2 degree greater angle at the rear. In this case, try adding 1/2 degree shim at the axle, but remember that any adjustment at the axle will alter the driveshaft angle, so you will need to go thru the measurement process again.
                        I suspect that you will find the engine is closer to 7 to 7.5 degrees, driveshaft 3 and axle -2, yielding a result of say 4.5, 0, and -5 degrees, which is where the factory recommends it to be.
                        If you want to approach it by jacking the rear axle at the differential, then jack it to level the drive shaft, but make sure that the jack isn't imparting some rotation to the axle housing.
                        Last edited by WCP; 06-06-2012, 10:03 AM.


                        • #13
                          I overlooked the fact that you have a GM engine rather that a Studebaker V8. So the engine angle may be a bit different as well as the preferred measurement location. However, the measurement and setup procedure remains the same with final angles less than 5, and 1/2 degree more at the rear.
                          My experience is with Stude powered drivetrains.


                          • #14

                            Thank you for replying.

                            I have, however, become even more confused - now. I was under the assumption that the angle of the driveshaft is irrelevant. A large number of reputable web sites never factor the driveshaft angle. The only angles they say that matter are that the angle of the engine/trans centerline matched that of of the differential (pinion) centerline. In essence the angle of the driveshaft becomes an irrelevant consequence of the other two angles. In example:

                            1. In a "broken back" like the Studebaker if the engine/trans was down -6 degrees (from "level") the differential (pinion) was also to be down -6 degrees (from "level"). Thus making the engine/trans and differential (pinion) centerlines merge (at a point in space) relative to the center of the driveshaft length.


                            2. In a more conventional setup if the engine/trans were down -6 degrees (from "level") the differential was up +6 degrees (from "level"). Thus making the engine/trans and differential (pinion) centerlines parallel to each other and in theory the lines never merging.

                            The numbers you give me are as you states from "the manual." So, it is difficult to dispute Studebaker, - but my brain just isn't getting "it."

                            I still can't get past the fact that the angle of the engine trans centerline - to the driveshaft, and the angle of the differential (pinion) - to the driveshaft are different. Shifting the numbers across a "zero-ed" driveshaft doesn't alter their relative angles being different even if numerically the become equal through this "zeroing" driveshaft process.

                            I'm not trying to be argumentative, I'm just confused. All this being said my angles are very close to those (factory) you listed - even if I'm not understanding them and maybe I'll just leave things were they are - maybe..., until my brain wrestles with me again.

                            Thanks, Tom
                            Last edited by wittsend; 06-06-2012, 03:07 PM.
                            '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


                            • #15
                              It is all about the driveshaft. The engine angle to the driveshaft should match the angle of the driveshaft to the axle. The angles are measured relative to a level driveshaft. In the so-called "broken back" configuration, Studebaker specifies that the rear angle be 0.5 degrees greater. Measuring the angle of the driveshaft and adjusting the other two angles accordingly, is easier than levelling the driveshaft physically.