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700R4 to TH400

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by josh86k10, Feb 20, 2005.

  1. josh86k10

    josh86k10 1/2 ton status

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    Well, I just paid my $25 so I figured I'd post my question in here since I can now:grin: .
    After 218K miles my 700R4 finally crapped out. I have found a miltary TH400 with converter, adapter, 32 spline 208, rear slip yoke, and front driveshaft for $400 5 miles from my house. I've been using the little search button and I think I've learned a few things, so I'll post what I think I know and ya'll correct me if I'm wrong. Oh yeah, truck started life with a 305, 700R4, 208 and I've put in a D60/14FF and a 6 inch lift with stock length driveshafts.
    So here's what I think I've learned:
    -only 3/8" length difference in TH400 (shorter) and 700R so driveshafts will still work
    -stock crossmember will still work
    -computer wires to 700R4 can just be disconnected and tied out of the way
    -need to run vacuum to TH400 from intake manifold
    -need to purchase and install electric kickdown switch on gas pedal, should already have stuff to bolt it up stock
    -stock column shifter will work (indicator will be off though)
    -stock lines will work
    -stock flex plate will work
     
  2. sweetk30

    sweetk30 professional hooker Premium Member

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    need tcase!!!!!!! input is bigger 32 spline not 350/700 27spline. so there goes your driveshafts . unless you find a 208 from 400.
     
  3. josh86k10

    josh86k10 1/2 ton status

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    I have the T-case, TH400 comes with T-case and adapter bolted up as well as a slip yoke and front driveshaft just because he has them and can no longer use them. Thanks for the reply. So, since I have the T-case everything is just bolt in and go?
     
  4. Keith in CO

    Keith in CO Registered Member

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    kick down

    Rather than going to a gas pedal switch, many GM vehicles equiped with a TH400 used a kickdown switch which mounts on the intake manifold to the left side of the carb. When the throttle mechanism moves back, the switch rotates clockwise to engage the kick down. All you need is one wire to power and one wire to the electrical connection on the left side of the TH400. Cheap, easy and it works.
     

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