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TH400 to a NP208?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ol_grayfeather, Jan 19, 2001.

  1. ol_grayfeather

    ol_grayfeather Registered Member

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    Will a TH400 bolt up to a 208 transfer case? If not, is there an adapter I can get or do I need a different transfer case? It has a 700-R4 now but it not in good shape. Thinking this summer of putting a big block in my Blazer and heard the 700-R4 wont hold up very long. ( also have a friend with an '80's short box PU with a healthy 396 and destroyed 4 700's before going to a TH400 and 3/4 ton running gear)

    Thanks

    Dan '84 Blazer
     
  2. 454jimmy

    454jimmy Registered Member

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    no you dont want to run a 700r4 , i have an 85 Jimmy with a 454 and it is down right now because it killed another 700r. I am looking for a 400 and 208 myself from what I hear they came in 1 ton trucks . the 208 that I have wont bolt to the 400 cause I dont have the adapter plate and the 400 output shaft is not the same as the 700r. you can get an adapter kit that will let you put a 400 in place of the 700r but you have to change the out put shaft in the 400.
     
  3. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Anybody need a 400/208 adaptor? I have one for the pre-85 trucks. This is the tall adaptor.
     
  4. 78Blazer

    78Blazer 1/2 ton status

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    My 84 m1009 had a th400/208 also had a 6.2 diesel in it.



    Scott
    78blazer
     
  5. Smitty

    Smitty 1/2 ton status

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    I've got a TH400/NP208 in my 82. It's holding up well but I don't have any info on the install since it was there when I bought the truck. I'm told that it doesn't have the real low 1st gear like the 700.

    Smitty
     
  6. ol_grayfeather

    ol_grayfeather Registered Member

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    If they came in 1 tons, what years we they ofered and what all would I need out of the donor turck? Is the TH400/NP208 the same lenght as a 700-R4/208? We have a pretty good Junk yard around here "Pull and Save" I got a 350,TH350 tranny and a radiator for $230 about a week ago.

    Thanks
    Dan '84 Blazer
     
  7. thatK30guy

    thatK30guy 1 ton status Premium Member

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    The one tons everybody is referring to are the military trucks. The M1008, M1010, M1028, and M1031. These are all the one tons with either np205 or np208. Boyce Equipment would be your best bet on getting the correct parts. Factory one tons for GMC or Chevy for the public were equipped with np205's.
     
  8. turbo

    turbo 1/2 ton status

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    Easy to find.

    They came stock on early 80's 3/4 tons.
    for example my 3/4 ton 8600GVW burb can stock with M code 350 gas a TH400 and a 208.

    You only need a 4x4 TH400 the stock adapter and a 208 with the big input spline to fit the TH400 output shaft.

    All the early 80's except 81 3/4 ton 4x4 burbs have the Th400 208 but the 1/2 ton have the 700R4
    Just watch for the 8 lug burbs at the yard.
     
  9. redbeast

    redbeast Registered Member

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    I Have A question;
    Ive building 700s both early an late models for years now. Ive got them in pro stock,
    pro street. and and a bunch street rods all with some big horsepower numbers an lo et's.
    what's breaking on them, burning clutches. bands. sprags ? I jus wonder if the shops that
    go trough them are not building stoung enough ie kevalar clutches. kevlar bands, fairbanks
    servos and some good vb mods.. Im running one in my 85 that I rebuildt recently, shifts
    are nice and firm, temps are low. and ive put a switch on the lock up. Im allways looking
    for imput on problems that they have so I can come up for a fix.. Just one more comment
    the 700r4 is based on two different transs types the 4l60 is based on the th350 the 4l80
    is based on the th400.. I prefure the lock trans for the low first and the od ( i need the
    gas milage).. the 4l80e is the better trans of the bunch. not as common as 4l60. the
    E models are whole different world of problems, I wont go into them now.. jus my .02
     
  10. 454jimmy

    454jimmy Registered Member

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    redbeast
    this is what happens most of the time with the beast that i have. stock 700 backing up (trying to back up) a 454 that is a little more than stock , 33 in tires . 3rd gear always goes out , most of the time its after you stop and then take off . 1st gear then it will shift into 2nd and when it trys to shift into 3rd it wont go. I havent driven it in OD at all , from what I have been told that will kill them also when you run them in OD. what do ya think ?
     
  11. redbeast

    redbeast Registered Member

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    OK when you say 3rd goes out,is it all of a sudden or gradually. are you still useing the L/UP or is done away with, turned off, or using a th350 converter. They are several versions of the stock 3/4 clutch set up.
    some use 6 disc. some use 5 disc. They offer a 9 disc set up that is much stounger than stock they call them the no burn set up.. It uses a kevlar disc plates very stroung, resistes heat better. Im assuming that your rebuilder is also boosting the pressures with a good valve body reprograming kit. When you do not use the L/UP you are not allowing the trans to cool it self proparly, I know that it sounds funny but the trans will not by pass enough fluid to the cooler to keep it alive.. Why do you not use the OD ? thats the biggest asset of the 700r4..I love that extra gear on the hihay I can cruse at 60 mph at only 15k rpm helps mpg big time..They are lots of mods you can do to the trans to make it live.Problem is lot,s of rebuild shops wont do them. It takes a little to build them right for performance use, so they jus build the to factory specs an let them go. If your dead set on caning the 700 4L60 try finding The 4L80 instead its based on the th400 trans so its alittle strounger... Hope that helps.. RGee .. By the way heat kills auto transmissions. No matter which way you go invest in the biggest trans cooler you can stuff in the truck, a spin on filter is a good investment also.......
     
  12. ol_grayfeather

    ol_grayfeather Registered Member

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    OK Redbeast...... What would it cost to rebuild a 700-R4 to hold up to a mild big block? Just wondering if its more cost effective to go looking for a th400.

    Thanks
    Dan
     
  13. redbeast

    redbeast Registered Member

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    I get my parts from a local supplier in austin tx called Jerrys Transmissions, they take care of me so thats who i use. B&M trans missions sells practally every part that you can think of for the 700r4 (pervformance parts).. The last kit I bought from them was around 300.00 It came with all parts that you need to beef the transmission, even came with a ATSG rebuild manual.. Ive buildt that won to run in a 64 vette thats used in both 1/4 mile and SCCA racing.. Been 2 yrs now and still holding up.. I perfer to Raybestos cluches for plates and the kevlar 2/4 band.. Along with the fairbanks servos for added pressure in the 2/4 band aplacation.. The servos is around 60.00. the band is around 10.00 and the major rebuild kit is around 80.00.
    The rebuild may look scary but the book explanes every step clearly.. So dont let it beat yea.. Besides there is no better feeling than to feel the trans go the shifts knowing that you buldt it.. Bragging rites are nice too. I learned from the book and took off from there got about 100 units to date on the road..Besides I couldnt stand to pay someone else to do what I firqured I could do my self...Turn key rebuilds at trans shop are running around 1.500 around here,couldnt afford to pay that...I hope That helps you in your decison.. Bottom line is this make your self feel good no matter what every body trys to tell you.... Good Luck, RGee
     

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