Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

th350/np208 question

Discussion in 'The Garage' started by georgiared84, Dec 9, 2002.

  1. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    Okay, installed my new gm goodwrench 350 this week. New intake, same exhaust, new carb, etc.... Now I'm thinking, why didn't I blow up my 305 years ago. Now the question. My 700r4 is most likely on it's way out. (slipping between 1st and 2nd) and the overdrive is just a pain in the neck around North GA anyway. I have a th350 and a th400 in the garage. I'm planning on rebuilding the 350 to go in the blazer and keep the np208 behind it.Got to stay on a budget since I just dropped about 3000 into the engine. I know I need a different output shaft for the 350 to connect it to the np208. Who sells adapter kits to match a th350 to a np208, and will I be able to use my stock drive shafts from the 700r4/np208? I did a search but couldn't find the info I needed.I could really use some input from someone who has done this swap.
    Thanks!
     
  2. COCHEV

    COCHEV 1/2 ton status

    Joined:
    Jul 9, 2002
    Posts:
    4,055
    Likes Received:
    2
    Location:
    Washougal WA
    all you need is the correct output shaft and the factory adaptor for a th350/208 combo. 81 is a good year for this. not sure about the drivelines. only the tape will tell.
     
  3. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

    Joined:
    Sep 17, 2001
    Posts:
    1,962
    Likes Received:
    0
    Location:
    Western CO
    i have a th350 to np208 adapter ,and a bunch of other 208 parts .what is the th350 from ? if it is from a 2wd just shorten the shaft and walla . cant really help with the length tho . i do know that the 700r4 adapter is shorter the the th350 adapter , you could even use the 700r4 adapter if the shaft matches up .
     
  4. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    the 350 was out of a 4x4 but I don't know what year. The shaft is for a np205, but I'm rebuilding the trans. anyway, so It won't be any prob changing it out. Anyone done this swap? anyone...anyone... Buhler??? probably spelled that wrong. Anyone know how third geer on the 350 compares to third gear on the 700r4?
     
  5. Calclips

    Calclips 1/2 ton status

    Joined:
    Apr 4, 2001
    Posts:
    1,005
    Likes Received:
    0
    Location:
    Swartz Creek, Michigan/Flint while in school
    Could you explain "shorten the shaft and walla," I've got a th350 out of a 2wd van that I want to put into my truck as its rebuild was professionally done 2k miles ago. Are you saying I can take a saw and cut the shaft to the proper length and not have to tear the whole thing down to replace the output shaft?
     
  6. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

    Joined:
    Sep 17, 2001
    Posts:
    1,962
    Likes Received:
    0
    Location:
    Western CO
    that is what i am saying . what t case u gonna stick on it ? a 208 ? check the splines measure and do all the waste of time stuff before u do cut tho . Oh and you would be better off cutting it with a 4" grinder i think , they are really hard if i remember right ,just dont get it too hot .
     
  7. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    Still looking for someone who might know if I need to change driveshafts for the 700r4 to th350 conversion. I want to get everything set before I drop the trans since this is my daily driver and my other truck is in a coma until I build an engine. /forums/images/graemlins/1zhelp.gif
     
  8. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

    Joined:
    Sep 17, 2001
    Posts:
    1,962
    Likes Received:
    0
    Location:
    Western CO
    right now you have a 700r4 and 208 right ? the 700r4 is 1.5 " longer than a th350 , the t case to tranny adapter is shorter than the th350 to np208 adapter . i could go measure all this out sometime if ya want . just a guess but i think u might be ok on the drive shafts .
     
  9. COCHEV

    COCHEV 1/2 ton status

    Joined:
    Jul 9, 2002
    Posts:
    4,055
    Likes Received:
    2
    Location:
    Washougal WA
    measure your existing combo. and if remember, i'll measure my th350/208 combo. then we will see if there is a difference. /forums/images/graemlins/grin.gif remind me often cause i'll forget-on perpose /forums/images/graemlins/tongue.gif it's dark when i leave for work and dark when i get home. i'll try to remember to do it at work.
     
  10. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    I'll measure it tomorrow and get back to you on the length. Thanks.
     
  11. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    Sooo... You wanting to sell any of those parts? Trying to find the output shaft and adapter to match the 350 up to my existing np208.
    By the way, thanks for the info.
     
  12. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

    Joined:
    Sep 17, 2001
    Posts:
    1,962
    Likes Received:
    0
    Location:
    Western CO
    I have an extra adapter for sale if ya want . if it is a 2wd tranny i think u can just cut it to length , i dont have a shaft but i might be able to get one for ya . ill measure it out as i have an unmolested 2wd th350 . -Andy
     
  13. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    The trans is from a 4x4 truck. had a 205 adapter. I've got a trans. guy who's going to rebuild it for me. Is the shaft and adapter all I need to make it fit the 208? How much you want for the adapter?
     
  14. Fubeca

    Fubeca 1/2 ton status

    Joined:
    Dec 18, 2002
    Posts:
    2,100
    Likes Received:
    2
    Location:
    Denver Area
    I've done it the other way (swapping 700 for a 350) and it was pretty simple. The adapter you need is a GM part that is used on trucks with the 350/208 combo. It places your t-case in the same position as it is now with the 700r4 so the driveshaft lengths shouldn't change. The adapter is just about an inch or two fatter to take up the space that the shorter th350 creates.

    As I read this I don't know if it make any sense, let me know if you have any more questions /forums/images/graemlins/ooo.gif
     
  15. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

    Joined:
    Sep 17, 2001
    Posts:
    1,962
    Likes Received:
    0
    Location:
    Western CO
    yes the shaft and the adapter are all you need , well and 4 bolts haha /forums/images/graemlins/deal.gif /forums/images/graemlins/thumb.gif .

    hows 50$ plus shipping on the adapter ?if not lemme know ..
     
  16. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    Could you see what shipping would be to 30168?
    Thanks
     
  17. Pure Insanity

    Pure Insanity 1/2 ton status

    Joined:
    Mar 17, 2001
    Posts:
    4,579
    Likes Received:
    0
    Location:
    Dade City, Florida
    I have this set up in my Blazer. The Tcase stays where it is now, so the shafts remain the same. All it really is, is a spacer between the cast steel 208 adapter and the tranny. IIRC its about 3-4 inches wide. The bolt pattern is the same from the 350 to 208 so all thats needed for hardware is long studs. I "think" you can use a long shaft 350 and cut it to length, OR buy the kit w/ the shaft.
     
  18. COCHEV

    COCHEV 1/2 ton status

    Joined:
    Jul 9, 2002
    Posts:
    4,055
    Likes Received:
    2
    Location:
    Washougal WA
    Ok, my th350/208 combo is roughly 46" from the bellhousing to the end of the t case. hope this helps /forums/images/graemlins/grin.gif
     
  19. Pure Insanity

    Pure Insanity 1/2 ton status

    Joined:
    Mar 17, 2001
    Posts:
    4,579
    Likes Received:
    0
    Location:
    Dade City, Florida
    The Tcase and crossmember are in the EXACT same place they are w/ the 700 208 set up.
     
  20. georgiared84

    georgiared84 1/2 ton status

    Joined:
    Sep 5, 2002
    Posts:
    487
    Likes Received:
    0
    Location:
    Austell, Georgia
    Thanks, Mine is the same with the 700r4. That helps a lot.
     

Share This Page