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Doubler?

Discussion in 'OffRoad Design' started by Blazr77400, Nov 21, 2001.

  1. Blazr77400

    Blazr77400 1/2 ton status

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    Stephen,
    On your webside, it talks about the transmissions and the 203 you need to get to fit it. It says a th350 version of the 203 is easily adaptable to fit a 700-r4. What is needed to do so.
    Also, what front output did you use on you 205.
    Thanks


    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  2. Ryeguy

    Ryeguy 1/2 ton status

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    There's (at least) two ways to do this.

    1.) Spend big $ and buy a different output shaft for the TH700R4 from A/A. Then spend more big $ getting it installed into your transmission. And bolt up the NP203.

    2.) Spend a little bit of dollars and get a spacer (kinda like a donut with 4 holes, two alignment steps) made up to bolt between the TH700R4 and the NP203, and run longer bolts. And leave your TH700R4 alone. Means your drivetrain is about 1.25" longer (or so) than solution #1, but your bank account is lots happier.

    --Rob
     
  3. Blazr77400

    Blazr77400 1/2 ton status

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    What does the spacer do?
    Are the splines the same, just longer?

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  4. Ryeguy

    Ryeguy 1/2 ton status

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    The TH350 and TH700 share the same spline count (27). They also share the same (4-bolt) pattern that the T-case bolts to. The difference is the length of the shaft extending beyond the housing. You can't simply cut the shaft 'cause the splines don't exist far enough inside the case on the TH700R4. So a spacer simply spaces the transmission pattern back a bit to get the proper engagement.

    --Rob
     
  5. Blazr77400

    Blazr77400 1/2 ton status

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    I planned on just using one crossmember in front of the 205. I dont have a 203 to th350 marriage block. So when I make the spacer could I just add the locating steps, and the extra lenth to the spacer.That way I could get rid of one piece. Also, is the doubler adapter made of aluminum, If so Could I just build the Spacer out of aluminum.

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  6. blazer72

    blazer72 1/2 ton status

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    You can use one crossmemeber if you want but plan on the 700r4 case becoming 2 or more pices! The tork in 2 times what you have now and funny things with happen. Run 2 cross memebers and the side mount on the 205 that goes to the frame. The aluminum parts are not just soft everday aluminum nor is the spacer just a block it has sholders that line up the parts it spaces. Unless you do machine work every day buy the parts it will be cheaper in the long run.

    72 Blazer CST 400TPI NV4500 NP203/205
    01 Suburban 8100 2500 4X4
     
  7. Ryeguy

    Ryeguy 1/2 ton status

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    As 'blazer72' said, one crossmember likely won't be enough. Do it right or do it twice.

    We used "soft everyday" aluminum on a spacer for a Toyota running a 4.3L, TH700R4, NP203, NP205, no prob's. But the truck is relatively light, around 5000lbs. We could have made it out of steel, but the aluminum was handy and available. Agreed, for a heavier truck, steel or a high grade of aluminum would be better.

    I can ask my machinist how much to do another if you're interested. Definitely will be a fraction of the cost of a A/A TH700R4 output shaft.

    --Rob
     
  8. Blazr77400

    Blazr77400 1/2 ton status

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    I happen to be CNC machinist so it wouldnt be a problem to make it. Maybe out of 6061 aluminum, or 1018 steel.
    I ended up finding a th350-203 marriage block so I am going to use the Double crossmember setup.
    I talked to the guy who built my trans and he said the same thing about the 700r4 Braking into pieces. He said they were only made for aluminum transfercases. Thats why they are so weak.
    But with most everything else, seems like you have to brake it once before you know it isnt strong enough. (10bolt, 208 case, Neapco Splines)

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  9. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Way #3 Keep the NP208 adapter housing on the back of the TH700 and re-drill the face of the 203 to the round bolt pattern. Still longer than the "factory way" (using the short shaft and factory plate) but cheap and fairly easy.

    DO NOT DRILL ANYTHING ON THE NP203 WITHOUT THE DOUBLER ADAPTER BOLTED TO IT, YOU NEED IT TO MAKE SURE THE ROTATION IS CORRECT.

    I wouldn't be a bit concerned with using 6061 alum for anything in a drivetrain as long as it's designed reasonably well. It's pretty good stuff.

    I ran the Doubler for about a year with a single crossmember, but I just had 36" tires and still had the 10 bolt in front so I couldn't put a whole lot of torque to it. After that I ran the 2nd crossmember and liked the extra security.

    I'm running a 32 spline front output at this point, mostly so I have exactly the same shafts and connections for front and rear driveshafts. A 30 spline would work just as well I think, but what the heck it's stronger by a little bit and I use the same yokes and shafts front and rear.

    I ran a 10 spline front with no problems when I had the 10 bolt in front, and I know quite a few guys that wheel pretty hard with a 10 spline front even with a D60, but I think it'll catch up with them sooner or later.

    Making the world better, one truck at a time.
    SW-ORD
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
     
  10. Blazr77400

    Blazr77400 1/2 ton status

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    If I used the stock 700r4-208 adapter and redrilled the 203 case, would I still need a spacer, or even the A/A Output shaft for the 700.
    Also, what did the 32 spline front output shafts come on.

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  11. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    If you use the 208 adapter you don't have to change the shaft at all or use a spacer, it's just longer overall.
    32 spl. fronts came in fords and I think in some Dodges. The ones we use are all from Ford applications.

    Making the world better, one truck at a time.
    SW-ORD
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
     
  12. Blazr77400

    Blazr77400 1/2 ton status

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    I was reading an old Petersons 4wheel mag and came across the Gen. 1 Doubler. 1998. On the Cover it had that purple short bed chev. Anyway, It said that you could send you stock 203 shaft in for a Credit. Can you still do that and how Much is it worth.

    4 wheeling is like sex, when its good, its really, really good, when its bad its still pretty good.
     
  13. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    We're not taking core 203 shafts at this point, but it's not a bad part to hang onto. One of the problems is we have to be really picky. We don't want to re-work a shaft that's got wear on it so we look for basically new or actually use new shafts. If we continue using stock shafts, we may buy them back but it's not in the plans right now.

    Making the world better, one truck at a time.
    SW-ORD
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
     

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