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TH700 to TH350

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by blazerboy16, May 1, 2000.

  1. blazerboy16

    blazerboy16 Registered Member

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    My TH700 just went in my 89 blazer and i was wondering what kinda trouble i would run into if i swaped it for a TH350. i would appreciate any help.
     
  2. You are looking at higher RPM's without overdrive, which means hotter engine/tranny temps, and worse gas mileage. In an 89 you have the NP208 or NP241 and I am not sure of the bolt pattern or spline counts, so an adapter might be needed. I am eventually going to pull my 700 and swap in a TH400 and will just run a tranny and engine cooler with it to reduce the heat factor. To hell with gas mileage, I run 38's anyway !! I believe the TH350 is a heartier tranny than the 700R4 unless you go with the TCI or have someone do the same upgrades to it. Good luck !!

    [​IMG]<font color=red>BigBurb[​IMG]
    <font color=purple>IF YOU'RE SCARED, SAY YOU'RE SCARED !!
     
  3. turbo

    turbo 1/2 ton status

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    700R4 and 350 have same 4 bolt rear extension/ transfer case pattern

    Both 700R4 and TH350 have same output shaft spline.

    Will bolt directly to your TC but slight differeence in length means may need rear cross member and drafshaft length mods.

    As far as the TH400 it has a 6 bolt rear extension pattern and a larger 32 spline output shaft.
    That means need new TC case adapter and have to either get custom 400 outputshaft (don't think there is one although there is a 32 spline custon 700R4 output shaft for trplacing a TH400 with a 700R4) or have to change the input gear in the transfer case.
    I just put in a built 700R4 with adapter replacing a 400 in a 3/4 ton 82 burb.
    Try bowtie overdrives (they have a web site) and make quality 700R4s
     
  4. Jason73K5

    Jason73K5 1/2 ton status

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    Another thing to look at it the fact that your 700-R4 has a much lower first gear than a TH-350 does. Thats the main reason that I'm considering doing the opposite swap that you're planning. It just all depends on what tires and gears you're running, since you'll need more power to get off the line as quickly and will have to rev higher on the top end.
     
  5. What is the length difference in TH350 and 700R4? What was your 400 hooked to for a transfer?

    [​IMG]<font color=red>BigBurb[​IMG]
    <font color=purple>IF YOU'RE SCARED, SAY YOU'RE SCARED !!
     
  6. Brian 89KBlazer

    Brian 89KBlazer 1/2 ton status

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    Bigburb

    According to a Four Wheel Mag article with Steve Watson, 1.5 inches.

    Brian
     
  7. turbo

    turbo 1/2 ton status

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    Stock was a 82 4x4 burb 3/4 8600GVW so no cat
    350cid M code TH400 and a chain drive 208 (with the 32 spline input gear)
    Replaced with a 700R4 with speical 32 spline outputshaft and a 1 inch adapter plate between tranny ass end 4 bolt pattern and stock Th400 to TC stock 6 bolt adapter.
    Adapter plate and seals and output shaft sold as kit from advance adapters.
    Shaft installed by bowtieoverdrive.com.
    Total length with 1 inch adapter plate)identical to stock Th400 setup so motor mount and driveshafts just like they started.
     
  8. WELLH2O

    WELLH2O Registered Member

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    What does everyone think of the Turbo-700 that 4 wheel parts wholesalers has for sale. They say that they have done over 40 mods to boost durability and performance of it. I was thinking of going with it to replace my failing tranny in my 1990 full size blazer. Just want to know what the rest of you think.
     
  9. turbo

    turbo 1/2 ton status

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    I did a lot of looking around and the guy who was most knoledgable and had all the recomended mods with a very competive price and waranty was Steve at bowtieoverdrives.com
    He was the only guy who shipped instructions on how to adjust the TV cable for full piston travel by checking inside the tranny pan where it counts.
    They insist on a pressure check and call when you first start it up and walk you thru all the proper adjustments for a long tranny life.

    Byron
     
  10. '73 K5

    '73 K5 1/2 ton status

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    Keep your current style tranny. Lower first gear and overdrive. Who doesn't want overdrive???

    '73 K5
    Chevy good...Ford bad
     
  11. Brian 89KBlazer

    Brian 89KBlazer 1/2 ton status

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    WellH2O

    That's the JET Tranny isn't it? Unbeatable in a word. Haven't got one yet but I'm using either their kit or B&M's to overhaul my 700-R4 this summer. Both boost torque capacity to the 450ft-lb range. More than enough for most small blocks. There was a write up on them in a recent Four Wheeler article where their Project Blazer got a JET tranny and Off Road Design Doubler T-case conversion.

    Good Luck
    Brian
    Still in search of the TBI KING!!
     
  12. Thanks, I was reading the stats on trannies and the 4L80E is one tough tranny. Twice as strong as the Jet 700R4 !!

    [​IMG]<font color=red>BigBurb[​IMG]
    <font color=purple>IF YOU'RE SCARED, SAY YOU'RE SCARED !!
     

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