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spring over (rear axle)

Discussion in '40- & 55-Series Tech' started by rusmannx, Jun 22, 2003.

  1. rusmannx

    rusmannx

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    well...
    i've been running a skyjacker 4" lift for almost 2 years now.  my friend who just bought his 77 fj40 is looking at the same thing, and i'm thinking i'll just sale him mine for dirt, and spring my 72-40 over.
    if i go through with this i think i'll be asking a billion questions you have already been asked (because i couldn't find the answer already).

    this whole conversion will be done with me and a couple of friends, in a shop (virtually every tool in existance), and having never done one before.

    my first question is:
    is it necessary to rotate the rear axle to achive desirable pinion angles? if so how much? by what method?

    this will be done with stock springs (i still have the old ones),
    yes i've read all of the tech section on SOA and Traction bars.

    thanks for the help
     
  2. cruzer

    cruzer

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    This depends on if you want to run CV driveshafts or not...if no then just weld the perches on parrallel to the stock ones if you are going to run a CV driveshaft you need to rotate it so the pinion points at the tcase output.

    Stew
     
  3. rusmannx

    rusmannx

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    i'm confused.
    any diagrams or pictures would help.
     
  4. theferg

    theferg

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    I think it's like this: If you run CV drive shafts, then the angle on the pinion won't matter and you could just weld the new spring perches at the same angle as the old ones, only on top of the axle (no turning the axle assembly at all). If you run the stock drive shafts (which are not CV shafts) then you should rotate the axle so it points towards the t-case a bit. Otherwise--vibration, vibration, vibration. None of those tech articles said anything about it....? Hmmm. I'll see if I can find any hard evidence to support my thinking...
     
  5. rusmannx

    rusmannx

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    the subject was touched upon, but ther seems to be some level of dissagreement as to wether anything should be done, or if it should all be done together.
    i see where you are coming from now though.

    if one would decide to rotate the axle, how much?
    some have said that the axle side u-joint should point at the t-case, but i've also read that this specifically is wrong.
     
  6. Pete_S

    Pete_S

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    I JUST finished an SOA. I am a conservitive with this type of stuff so I kept the perches at the stock angle. :doh:
    Nobody really mentioned the fact that the universals WILL
    "kn-uck" without changing angles and or some serious grinding/fitting on various stock drive line components. (If it matters, it's a 74 drivetrain in a 66)
    Where would someone get a CV driveshaft from to "fit" a Cruiser? Is this a "Taco" application with moderate length changes?
    Please don't use the word "cu$tom",............. please!
     
  7. TonkaC

    TonkaC

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    I did an SOA on my '70. The rear pinion I angled straight at the t-case. I ran the stock driveshaft till I could afford a new one. This set up will work but will vibrate quite a bit. This will lead to t-case bearings ,seals, and u-joints wearing out faster than normal. Once I could afford the new rear driveshaft from "Tom Wood's" with a CV joint at the top there was an instant improvement of the vibration. I replaced the rear seal of the t-case and it hasn't lost a drop of fluid sense. IMHO this is the best way to put the rear axle. I'm still running stock running gear (engine, tranny, t-case)
     
  8. rusmannx

    rusmannx

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    can a person just go to napa and buy any old heavy cv joint and make there own shaft?
    or do i have to buy someone's prebuilt expensive one?
     
  9. MD11Fr8Dog

    MD11Fr8Dog CM09 Eight Ball winner

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    Hmmm, I think you have this wrong.

    If you do not rotate the pumpkin to point at the tcase, then you need to make sure that the pumpkin and tcase flanges are parallel - the U-joints will cancel each other out during rotation! If you point the pumpkin at the tcase you will need a CV. This may be required due to the highth diff between the pumpkin and tcase flanges and the lenght of the required drive shaft etc. By pointing the tcase at the pumpkin the 2 u joints will be out of phase, hence the require for the the CV (which also allows for high angles!) to eliminate possible vibration due to the u-joints being out of phase!

    Here are a couple of links

    http://www.geocities.com/benmlee/u-joint.htm
    http://www.custompistols.com/cars/articles/ts_ujoints.htm
     
  10. TonkaC

    TonkaC

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    can a person just go to napa and buy any old heavy cv joint and make there own shaft?
    or do i have to buy someone's prebuilt expensive one?


    There is a junkyard in my area that has several driveshafts that have CV joints on them. If you check a junkyard by your home you might be able to find one for yourself. You would still have to get the flange re-drilled, or the studs on your e-brake drum moved so they could be bolted together, and the length changed. If you had all this done, new u-joints, lengthened, mated to your rear flange, you will be running up the price. Just be careful when doing this so you don't end up with a shaft that is inferior and costs almost the same as a good one.
     
  11. axlechassis

    axlechassis

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    there are essentially two ways of going about spring overs.
    1. the cut and turn method: this is the best way if you want to retain the stock wheelbase.
    2. the spring rotating method: cheaper to do than the cut and turn. Lengthens the wheelbase about 6" which helps the driveline angle issue. The longer wheel base addresses the highway stability issue too.
    there are lots of posts on this subject. I've posted several times on it.
    say what happenned to the picture posting thing?
     
  12. axlechassis

    axlechassis

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    THIS IS JUST PLAIN WRONG
    I can see how spring overs can get confusing with boneheads like this offering completely wrong information. This the second time I've noticed this guy posting nonsense.
     
  13. theferg

    theferg

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    Sheesh, no need to get so huffy-puffy there.  First off he's talkin' about the REAR axle.  I know all about the cut-n-turn for the FRONT (unless you cut-n-turn the rear   ::) ).  And, ya, after searchin' around a bit and thinking about it, I realize I had the info messed up about the rear--basically oposite what I said.  No need to start calling names here and discounting every bit of info some one has ever written.  Sorry, not ALL of us are right 100% of the time....
     
  14. rusmannx

    rusmannx

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    you guys rock!
    i hope no feelings are getting steped on to harshly over my stupid question.

    i've decided that u-joints need to be running parallel for the following reason.

    when a u-joint (lets say the t-case side) is at some angle (lets call it theta) the joint itself accelerates as it spins  (because any change of direction [like something spinning] is acceleration by definition).  if the axle side u-joint is at some angle other than "theta" (or at no angle at all) the veocity of the joint will be different then the one at the t-case.  these two different changing velocities (at opposite ends of the driveline) ARE different accelerations (again by definition) and this is what causes the vibration (typically at the t-case end if the axle side u-joint has been rotated to far away from parallel).

    i guess i should have thought of this (being a mechanical enigneering major and all) before i started stirring the hornets nest.  
    thanks for the help guys.

    please correct me if my thinking is incorrect.
     
  15. Medusa

    Medusa

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  16. axlechassis

    axlechassis

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    What!!! did being called a "BONEHEAD" Hurt your feelings? well excuuuuuusssse me. Maybe you should just post about things you know about and this issue wont ever come up again. Have you ever done a springover to a cruiser?  I think not. If not shut up and let those of us with practical hard earned experience speak. Again this is not the first time you've been called to the mat.
    I guess I'll have to change my name to axle-nasty or quit drinkin lysol
     
  17. ScottFJ40

    ScottFJ40

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    Dang, I thought I was reading Ih8mud, but it looks like the PBB in here. ::)
     
  18. woody

    woody Internet Fireman Staff Member

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    Rule: when you personally hit perfection, then you can criticize the rest of us for not being perfect.
     
  19. Gumby

    Gumby Supamod Staff Member s-Moderator

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    Dude,
    Both your posts had wrong info, the difference is the theferg said "I think" and "let me check on that" and you just ranted. I think I have seen almost anyone who volenteers info on this forum and others post incorrectly once in a while. It happens.

    Less caffine and more :beer: for all!
     
  20. axlechassis

    axlechassis

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    Ok I'm sorry. (sincerely this time). I'll try to be nice from now on. and quit drinking lysol! 8)