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Best PS Gearbox for Saginaw

Discussion in '40- & 55-Series Tech' started by FJKen, Aug 26, 2003.

  1. FJKen

    FJKen

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    I'm prepping for a PS conversion on my '76 FJ40. Got a gearbox from a 1986 Blazer, but I'm hearing that it's better to use the gearbox from a GM car due to the superior number of rotations. The Blazer box gives me 3.5 turns, which should be ok. Anybody got any experience with using a GM box from a truck v. a car? How many rotations from a GM car gearbox?

    Thanks fellas!! :D
     
  2. wheelie

    wheelie

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    not sure, but i think the reason ya use the ps out of a car is because it mounts to the inside of the frame. where most conversions mount to, guess ya coud do it on the outside but why?
     
  3. hammerhead

    hammerhead

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    Wheelie is right. The truck box mounts on the outside of the frame and unless you are using full size axles you dont have room. The 4x4 truck box has the additional problem of the arm working in the wrong direction. GM 4x4s have a strange arrangement where the steering box accuates front to back. The car style sag box mounts inside frame thus not interfering with front wheel clearance. It also has the arm pointing rearward for left and right steering travel. Also, if you look hard enough, you can find the big brother to the 3 1/8" piston car sag. It is a 3 1/2 " piston sag in the same casting.
     
  4. FJKen

    FJKen

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    Thanks Wheelie..the ps box from a truck looks the same and mounts just as the ps box from a car. I believe it's just the internals that are different in that a truck box doesn't have the same number of rotations. I'm just wondering if anyone has used the box from a GM truck or SUV and had success.
     
  5. FJKen

    FJKen

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    Thanks Hammerhead! I'll go check out the box from the Blazer but from what I remember it doesn't look much different from a GM car box. It mates up nicely to the scab plate that's part of the Downey kit that gets welded to the inside of the frame rail.
     
  6. hammerhead

    hammerhead

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    Look again dude. I just finished a cross over steering on a blazer and they dont use the same box as a car. It is a mirror image. The mounting points are on the opposite side.
     
  7. FJKen

    FJKen

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    Hammer.. I looked again. The 1986 Blazer box looks good. The spline facing the frame rail with the pitman arm on the bottom and the flat mounting side mating up with my scab plate that mounts on the inside frame rail on the driver's side. Is it possible that the '86 Blazer used a different box?
     
  8. FJKen

    FJKen

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    or... I've got a mislabled ps box from the junkyard!
     
  9. theo

    theo

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    [quote author=FJKen link=board=1;threadid=4657;start=msg35216#msg35216 date=1061918178]
    or... I've got a mislabled ps box from the junkyard!
    [/quote]

    Which way does the pitman shaft turn when you turn the input shaft? If that is correct you should be OK. But some GM boxes were mounted behind the front axle and have "reverse" rotation (i.e. pitman arm mounted pointing forward instead of back.)
     
  10. 78 One owner

    78 One owner

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  11. Gumby

    Gumby Supamod Staff Member s-Moderator

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    except an astro was mounted pointing up and down in front of the axle, but yeah, it turns like an Astro van. :D
     
  12. FJKen

    FJKen

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    Looks like the box is ok. I think Hammer is right about the Blazer box..at least from what I'm hearing. The box I have is marked "4 x 4", Blazer 1986. I have no idea if that is correct, but it looks like every other auto GM box I have seen. The conversion starts tomorrow, so I guess I'll figure it out real soon...