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drive shafts are wrong length, SM420 swap

Discussion in '40- & 55-Series Tech' started by pablo, Jun 29, 2003.

  1. pablo

    pablo

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    Okay, so I took apart my 73 domestic drivetrain apart and found that the the original 3 speed is much shorter than my SM420 by about 2.250" from face to face. The drive shafts will not work with that set-up especially when the adaptor plate is installed. The rear is slightly shorter than the front drive shaft so there is no potential for a front/rear drive shaft flip. I started this project with the assumption that I did not need to get replacement drive shafts. How much can I gain from a spring reversal where I move the front of the rear spring to the rear? Where can I get a longer OEM front shaft? I intend on using the original 3 speed t-case.
    Thanks
    Pablo
     
  2. rusty40

    rusty40

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    the front driveshaft from a 4speed is much longer than the 3speed you could probably switch the axle pinion flange with a 4spd one and use the three speed one at the tcase end

    I think that the toyota 4speed is pretty close to the same size as the sm420 with an adapter

    worth looking into?
     
  3. Cruiserdrew

    Cruiserdrew SILVER Star

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    Once you are done with your conversion, just get the driveshafts cut or lengthened as needed at a driveline shop. You don't need new shafts. Expect to pay about $75 per shaft for this work, less on the front if you don't have it balanced.
     
  4. 73lndcrsr

    73lndcrsr SILVER Star

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    I am about to do the same conversion. &nbsp:Do you have an tips that will help me? Which adapter plate did you use?

    Thanks for any help you can give.
     
  5. pablo

    pablo

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    73lndcrsr,
    I got a space ghost plate in the mail right now. This conversion is way too easy other than the drive shafts, so far. I have not had to fight a nasty gasket or worn out parts yet. I actually am taking pictures of the everything and might put everything up on the web. When I started I had a bunch of questions that are all answered now and I think it is smooth sailing from here.
     
  6. 73lndcrsr

    73lndcrsr SILVER Star

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    sounds good.

    Do you have the N307LOE bearing yet? If so, where did you get it?

    Thanks.
     
  7. pablo

    pablo

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    73lndcrsr,
    On the transmission swap section of the tech section one of those links mentions a source for that bearing, I could not find it again though. There are bearing houses in most major metropolitan areas. The place that I got mine from was an outfit in Texas. I looked them up on the web. If I was not helpful enough email me about it and I will check the receipt it is in the garage.
    Pablo
     
  8. 1980FJ40

    1980FJ40

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    Pablo,
    Would you please post about the bearing?!
    Thanks,
    1980FJ40
     
  9. pablo

    pablo

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  10. 1980FJ40

    1980FJ40

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    Thanks Pablo! How is the swapt coming? Almost done??
     
  11. SpaceGhost

    SpaceGhost

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    I haven't been here in a while so I missed this thread till today. Driveshaft mods are something you have to determine after the swap. I know that it is frustrating not to have all the parts, and knock this out over a weekend, It's just not that kinda swap.

    As you found the three speed is the shortest of all the trannys. I had new shafts built using spicer slip joint which is longer (6" or so) and 1310 joints, with a conversion flange that has the same pattern as the three speed pinion/tcase flanges. All new stuff, and less than $260.

    I have 2 shafts with the correct bolt pattern. One is an (all new unit) spicer slip, the other a long travel slip (12 ") I posted them for sale here a while back, but since I can't use them, the price will be very reasonable.
     
  12. pablo

    pablo

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    Space Ghost,
    Yeah, I think that I should just move the axle back the correct amount. I am thinking about using a spacer up front between the pinion flange and driveshaft. However, this is more experimental and probably too dangerous in the rear. Any ideas appreciated. Oh, the last option is to just make one on a lathe and tig weld it all. I could impliment a junk yard tube from an FJ-55. However, the hard part is holding the U-joint yoke centered. Again any ideas appreciated.
    Pablo