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SOA question?

Discussion in '40- & 55-Series Tech' started by 74bogger, Aug 6, 2003.

  1. 74bogger

    74bogger

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    ok i am thinking about doing a SOA on my 74 fj40. my question is about how to get the front pinion angle right. my idea was to set the ale on block with the spring perches flat on the block then set the new perches on top, make sure they are pefectly level then weld them in place. will this work? i am going to try to get some fj55 springs to use but will prolly have to use the stock springs for now any feedback would be appreciated
     
  2. woody

    woody Internet Fireman Staff Member

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    are you going to cut and rotate the housing? If no, then set the perches parallel or you'll have steering problems. If yes, then your description is right...

    I had mine under the rig 5 times before I was pleased with the rotate angle and pinion angle. Weight on the rig is the only way to test.

    IMO, if you are doing a shackle reversal, the cut-rotate is a "must do"...if you are leaving the shackles in the stock location, it's recommended but not required.
     
  3. hammerhead

    hammerhead

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    I SOAd my 74 with the old "saggy" stock springs and love it. In theory your plan will work. Your steering angles will come out correct but you will have the same problem I did. Your U-joints will bind. You will have to "clearance" the yokes to achieve angles past there design limits. It worked on mine but it is absolutely not the most desireable method. I am going to redo mine using the "cut and turn" method where the steering knuckles are cut loose and rewelded at the proper angle after the pinion is rolled up to match driveline angle.
     
  4. 74bogger

    74bogger

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    thanks for the info but im also going to use either fj55 springs or reverse the stock springs so this will lessen the angle of the drivshaft but will it be enough?
     
  5. woody

    woody Internet Fireman Staff Member

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    question is, are you doing the shackle reversal? IMO, thats the critical....reversing springs helps the angle some...but doesn't matter on shackle reversals
     
  6. 74bogger

    74bogger

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    yes i will be doing the shackle reversal and i already know tat im using 55 springs on the back but not sure about the front
     
  7. woody

    woody Internet Fireman Staff Member

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    if you don't cut-turn the knuckles with a shackle reversal, there is a 95%+ chance you will have driveshaft binding issues....with the shackle reversal, the pumpkin rotates the flange down on extension, and binds. Pop goes the u-joint or the pinion. No reversal, and the pinion rotates up on suspension extension, and the issue is greatly lessened.

    also, be prepared for an expensive front driveshaft....my front SOA with FJ55 rear packs and a custom shackle reversal uses about 5" of shaft stroke during normal trail use and on uphills where the front end "pulls" up and away, about 7". $400 for a shaft...roughly...
     
  8. 74bogger

    74bogger

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    roughly how much does the cut and turn cost to have it done? there is no way i could do it myself
     
  9. woody

    woody Internet Fireman Staff Member

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    IMO, it's not tough....angle grinder with a thin cutting blade, ocy-acet torch, and something to turn it with...see the pics on pirate or on my writeup for ideas.

    You outta find someone to do it for $150-200 exchange. (send yer empty housing for a core) There are a couple on the PBB that do it, plus lots around the country, including the guy who did mine.
     
  10. 74bogger

    74bogger

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    quick question on the end of the axle tube where the knuckle is, is the knuckle on a smaller diameter pipe that fits inside the axle tube and all i have to do is cut throught the weld and spin it ?
     
  11. rusmannx

    rusmannx

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    why can't you just have your drivelines lengthened?
     
  12. woody

    woody Internet Fireman Staff Member

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    [quote author=74bogger link=board=1;threadid=4139;start=0#msg30715 date=1060200396]
    quick question on the end of the axle tube where the knuckle is, is the knuckle on a smaller diameter pipe that fits inside the axle tube and all i have to do is cut throught the weld and spin it ?[/quote]

    Yeppers...you cut just at the inner edge of the weld, and only thru the outer housing. The knuckle itself sleeves about 2-3" into the housing, and you simply spin on that axis. Make sure you scribe a mark prior so you have a reference.

    Also, if you "screw up", any front housing from a FJ40-45-55 from 1982 back to 1969 will be useable....just in case...hehehe It is hard to see the splitting line when you are deep enuf...some require LOTS of heat/leverage to turn, I've heard others turn by hand once cut. Mine was a major PITA....which is why the guy who did mine created a custom hydraulic jig this past summer to make it easy...
     
  13. 74bogger

    74bogger

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    sounds easy to do so i think im gonna try it and if i doesnt work out then ill have someone else do it but now that i know that i think i can do it thanks for the info
     
  14. 74bogger

    74bogger

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    the reason you cant just lengthen the driveshaft is that when you put the spring on top of the axle, it make the driveshaft at an unacceptabe angle and it will bind when the suspension "works" and will cause the u-joints or even worse the pinion to break
     
  15. woody

    woody Internet Fireman Staff Member

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    [quote author=74bogger link=board=1;threadid=4139;start=0#msg30742 date=1060213072]
    the reason you cant just lengthen the driveshaft is that when you put the spring on top of the axle, it make the driveshaft at an unacceptabe angle and it will bind when the suspension "works" and will cause the u-joints or even worse the pinion to break
    [/quote]
    exactly...plus, with the shackle reversal, the pinion points down on extention, making the angle worse.

    Minitruck shafts have more slip than Cruiser shafts, but still not enuf.
     
  16. 74bogger

    74bogger

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    where should i go when i go to get another driveshaft? because im goin to do the reversal and SOA and im gonna cut and turn the housing
     
  17. 74bogger

    74bogger

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    another question what should i set the front and rear pinion angle to?
     
  18. hammerhead

    hammerhead

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    Woods says the pinion angle should match the driveshaft angle with the vehicle sitting on its wheels at the "normal" vehicle ride height. The rear shaft must have a double cardan or CV type joint at the transfercase. The front only needs double or CV if you run 50+ in 4WD.
     
  19. axlechassis

    axlechassis

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    Are you doing a a shackle reversal with a spring over? If so why? Is'nt the shackle reversal meant to improve the sua. The shackle reversal was the hot trendy ticket until recently. The jury is still out on it. A down and dirty cheapo soa with a spring flip still seems like a very viable option for those of us on tight budgets. There are alot of rigs running around with the cheapo soa sans problems.
    Also I know of a rig that works just fine with a soa, a shackle reversal and no cut and turn that works just fine, he is an older v8 conversion, that may be the difference.
     
  20. woody

    woody Internet Fireman Staff Member

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    My front shaft is a long travel, no CV from Tom Woods, http://www.4xshaft.com and my rear is a minitruck CV from High Angle, http://www.highangle.com I have no complaints with either one, but Jesse at HA has been using stronger Toyota joints in his and IMO, I'd lean that way for that reason.

    I did the shackle reversal for a variety of reasons, but the important ones are it reduced the chance of bending front springs and improved approach angles.

    If you point the rear pinion at the t-case output, then a CV is required. Usually necessary on shorter rear shafts. If you end up with more length, then you can set flanges parallel and not have issue. See Wood's site above for some great tech reading on shafts and angles.

    My front pinion points at the t-case. I always unlock my hubs for any road use, so no problems with vibration.