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Th350 Dana 20 Help

Discussion in 'Jeepster Commando and Commando Tech' started by Elijah Oldham, Aug 1, 2018.

  1. Aug 1, 2018
    Elijah Oldham

    Elijah Oldham New Member

    Kentucky
    Joined:
    Jul 15, 2018
    Messages:
    8
    New guy here. I just recently purchased a '66 commando. I'm rebuilding the 225 Dauntless and want to swap the transmission to a th350. I'm wanting to keep my Dana 20. I've found plenty of 2wd BOP 350's I can pick up. I know Novak has adapters, but I was wondering if there was another, I guess "cheaper" solution to adapting a th350 to a dana 20. Will a 4wd th400 tail bolt onto a th350? What about the shaft? Would you guys advise the th400 over the 350? I know its supposedly stronger, but it also takes more horsepower. I'm just trying to build a good daily driver that may occasionally go off-road.

    Thanks!
    Elijah
     
  2. Aug 1, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    May 25, 2006
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    400 bolts up with original Jeep parts. Fewer driveline issues then a 350. I have been running 400s behind Buick v6s for over 30 years and never noticed any HP loss issues. That is just numbers in a book that mean nothing in real life driving.
     
  3. Aug 2, 2018
    masscj2a

    masscj2a Sponsor Sponsor

    Chester Mass
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    Dec 27, 2013
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    Welcome Elijah. Daryl is correct. There might be a little parasitic loss with the 400, but hardly anything you would notice. I have both the TH350 in a V8 CJ6 and an even fire 231 with the 400. Both excellent choices in my opinion. I also like the SBC 327 with the early TH700R4, in a Scrambler. (non computer controlled) But either of those choices will work great.
     
  4. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Welcome Elijah, from northeast georgia
     
  5. Aug 2, 2018
    Keys5a

    Keys5a Sponsor Sponsor

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    The TH400 has a 6 bolt flange at the rear of its case, and the TH350/700R4 has a 4 bolt flange, so they don't interchange. Some of the later 4L60E models might have gone to the 6 bolt flange.
    The factory Jeep TH400/D20 combo has a unique spline and length on the output shaft of the transmission where is mates to the D20. There likely won't be a noticable difference in parsitic losses between the TH400 and TH350. GM's 200R4 was known as the most fuel efficient automatic non-electronic transmissions, but I not aware of any conversion plates/shafts to mate a transfer case to one.
    I would stick with the TH400/D20 factory combination. The 400 is bullet proof!
    -Donny
     
  6. Aug 2, 2018
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member Sponsor

    Denver, CO
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  7. Aug 3, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    Yes but not hard to find a 400, adapter and a 20 for less then this adapter by itself.
     
  8. Aug 3, 2018
    mikieboy

    mikieboy Member

    Jacksonville, FL
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    Mar 21, 2005
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    151
  9. Aug 5, 2018
    Elijah Oldham

    Elijah Oldham New Member

    Kentucky
    Joined:
    Jul 15, 2018
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    8
    Thanks for the advice everyone, I've got my eye on a TH400/Dana 20 combo at my local salvage yard.
    In relation to all this, what about a 700R4/Dana 300 combo or even Dana 20? JB Conversions has an adapter for the 300.
    www.jbconversions.com/products/adapters/1001.php
    The OD of the 700r4 is very appealing.
    How difficult would it be to just modify a factory 700R4/NP208 adapter to the Dana 300? I know all six holes won't align.
    If it isn't obvious I'm quite undecided as to what I want to put behind the 225, I even thought about a T-10/Dana 20 combo with some OD unit.

    I just want a good setup that is gets me decent fuel efficiency and can be sourced relatively easy and cheap. That's probably wanting too much. I don't care to pay for an adapter if I have to, I figure that it will ultimately pay for itself. But I'd love a less expensive alternative. And I really want an automatic over a manual, for ease of daily driving and because I'm 6'6" and leg room is appreciated. (Low gears can be annoying.) If you all have any suggestions throw them my way!

    Thanks!
    Elijah
     
  10. Aug 6, 2018
    jackdog

    jackdog Member

    Finger Lakes NY
    Joined:
    Jul 16, 2013
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    203
    I have a complete TH400/D20 setup with all adapters if your interested. Located in NY 14824.
     
    OrangeCJ5 likes this.
  11. Aug 6, 2018
    Elijah Oldham

    Elijah Oldham New Member

    Kentucky
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    I appreciate the offer, but you're a little too far away from me.
     
  12. Aug 8, 2018
    masscj2a

    masscj2a Sponsor Sponsor

    Chester Mass
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    If you were running a V8, I would go with a 700R4 and 300 TC, if you have the overall length to do that. But if your going to run the 225, I think the 400 with a Dana 20 would be all you needed to run. The Dana 20, is likely one of the top 4 or 5 transfer cases ever made, in my humble opinion. With the 1 1/4 inch intermediate shaft, its a hard one to break. Then you could find a flanged , centered Dana 44 rear end and have a great combo.
     
  13. Aug 8, 2018
    Elijah Oldham

    Elijah Oldham New Member

    Kentucky
    Joined:
    Jul 15, 2018
    Messages:
    8
    Well in light of popular opinion, I think I'll just do the th400/dana 20. However a Warn 25% OD unit might be in the mix.
    Thanks for all the input!
     
  14. Sep 3, 2018
    jim warren

    jim warren Member

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    Mar 13, 2012
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    144
    Last time I looked on Herm The OverDrive Guys website, he mentioned used adapters. They really don’t wear out and it will save you some cash.
     
    Keys5a likes this.
  15. Oct 1, 2018
    fhoehle

    fhoehle Sponsor Sponsor

    Eynon, PA
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    Apr 11, 2012
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    713
    For future projects, would you pm me with a price. I’m in NE PA so driving to the finger lakes is a short drive
     

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