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np208 to np205 conversion

Discussion in 'Chevy Trucks' started by 400hp408sb, Dec 13, 2006.

  1. 400hp408sb

    400hp408sb Junior Member
    from Maine
    Messages: 25

    My 87 3/4 chevy came factory with th400 and np208. I just recently went from 4 to 6in suspension lift and now require a longer rear drive shaft. Figured since I need a new d/s anyway and would like to get away from slip yoke style, and i found a np205 for $150, I would just swap it out. My concerns are the following.
    1. Does the shifter come through the same hole in the floor as the 208. I have a B&M ratchet shifter just to the left of the current hole now and not willing to move it.
    2. Does the speedo cable connect the same way or will there be any issues.
    3. Crossmembers. I imagine they require different setups but does the 205 style use same holes in frame or will I need to drill new ones
    4. From what I've read my th400 should have a 32 spline output shaft. Do I HAVE to have a 205 that was previously mated to a th400 or is it just a matter of buying an adapter? Or is the 205 easily/cheaply converted to a 32 spline?
    5. Is there a tag/stamp somewhere on the 205 case that would indicate production year and such?

    I'm sure I'm forgetting something. I apologize if I'm beating a dead horse here. I did a forum search but didn't find anything that was quite like my setup.
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Before I get into alot of detail about this swap I need some more info,first judging by your post the 205 you have isn't from a T-400 tranny,is that correct? If not you've got alot of work to do as these 205 swap's can be very confusing and the correct factory piece's to connect the trans and T-case can be very hard to find.Can you tell by looking at it what it's from? Yes, your tranny will have a 32 spline output but if the 205 is from a 4 speed or a T-350 it'll have either a 10 (4 speed) or 27 (T350) spline input shaft so thats no good.As to the year of the T-case,it should be cast into the main case on the front near the shift rails.The date will look something like this: D-23-7.Wire brush it real good and you should find it. Let me know and I'll be able to help you more as I've done many 205 swap's.
     
  3. 400hp408sb

    400hp408sb Junior Member
    from Maine
    Messages: 25

    Thanks for such a quick response. I don't actually know much about the vehicle the 205 came out of, other than it's an '84. But don't know if it was original. And I haven't bought the case yet. A friend at work is selling it and I'm going to go look at it this weekend. He "thinks" it was behind a th350. And "thinks" it was a slip yoke style, in which case I probably wouldn't be interested. But I'll buy it if I see it and find it's all the right configuration. I was looking for a heads up as to what issues I'll be dealing with in the conversion, if i go through with it. Sorry for the lack of info. I'll see him today and try to ask more. Another concern I just thought of is I'm assuming my tranny has a longer output shaft and i think the t400/205 combo used a short trany output shaft. Thanks again for your reply
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Yep, your right on the thinking that the outputs shaft's are different length's.If you go through with this swap you'll have to pull you T-400 out and have it completely disassembled in order to change the output. That's another reason why I said these can be alot of work to swap in.Keep me posted.... :nod:
     
  5. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    1 stop shoping and info needs for the chevy truck stuff. = www.ck5.com

    i have the same user name.
     
  6. hesko1

    hesko1 Member
    Messages: 45

    np 205

    AAA AH, I Have done this conversion many times, as a matter of fact I just did one yesterday. #1 The tail shaft out of your trans needs to be sticking out 2 3/8 inches.

    #2 The np205 needs to have the 6 bolt pattern on the adapter to match the six bolt pattern on the trans .( Any np205 off a th350 will have a 4 bolt adapter. )

    #3 The np205 needs a 4 bolt flange for the front drive shaft for your '87 ( Your front drive shaft will have to be shortened in this conversion also.)

    #4 If the np205 has a rear slip yoke It can be changed with a rear u-joint yoke out of either a np205 from a th350 or th400.


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