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2wd TH400 ?

Discussion in 'The Garage' started by SF87K5, Jan 26, 2003.

  1. SF87K5

    SF87K5 1/2 ton status

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    If you take off the tailshaft will a TH400 bolt to a Tcase. This is for a friend and I dont know the answer. I figured I would ask someone who would know so I dont look like an idiot and true to guess.
    Thank you for your help.
     
  2. ZonkRat

    ZonkRat 1/2 ton status

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    You have to use output shaft from 4X4 trans as 2WD is to long.The internals and cases are same .Look for 400{475} from class A motor home and some 1 tons.475 has straight cut planetaries and lower first gear,makes it wine a little in first,but it's stronger cause it doesn't transfer load to case like helical gears. /forums/images/graemlins/crazy.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/thumb.gif
     
  3. u2slow

    u2slow 1/2 ton status

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    Here is a tidbit from Offroad Design with three different "stickout" lengths. On a 2wd TH400, just measure from where the tailhousing bolts on to the end of the spline. It should be the 4.5" stickout version.


    GM TH400 Automatic Transmission:
    If you have a TH400, there are three options for mating the 203 to your trans.

    1: Use a factory configuration. The TH400 was available with the NP203 in heavier duty trucks (3/4 and 1-ton generally) in approximately '78-'79. The factory configuration uses a 1 3/8" stickout 32 spline shaft in the TH400, a 32 spline input gear in the NP203 and a 1.1" adapter plate between the two, somewhat similar to the TH350 adapter plate. This is the shortest way to mate the TH400 and NP203.

    2: Use a TH400 that originally had an NP208 mated to it. This TH400 uses a 32 spline shaft that sticks out of the case about 2.5" and has an adapter housing that's about 2.5" thick. You'll use a TH400 version 32 spline input gear in the NP203 and re-drill and tap the face of the NP203 with the round bolt pattern to match up to the NP208 adapter housing. Benefits of this kit are the parts are quite common since the NP208 was very widely used with TH400 trannies. The drawback is the adapter is about 1.5" longer than the shorter factory configuration.

    3: Use a TH400 that originally had a NP205 behind it. This TH400 uses a 32 spline shaft that sticks out about 4.5". You'll need to use a factory TH400 to round pattern NP205 adapter housing that is 4" thick and once again, re-drill the front face of the NP203 to match the round pattern. The input gear will be the TH400 version NP203 32 spline input. Drawbacks to this system are the overall length with the 4" housing between the two and the expense of buying the factory housing. They're not common as used parts and typically must be purchased new. ORD can supply this adapter.
     
  4. trukman1

    trukman1 1/2 ton status

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    Danny, I used a short shaft 2wd tranny when I converted to TH400/NP205 with no problem. Ordered the adaptor from www.4xHeaven.com in NY. Had to open the input bearing hole in the transfer case since it was off a 465 and needed a larger bearing, also from 4xHeaven. Called and got all the parts at a good price and all the free advice anyone could want. They never failed to answer any questions I had. Contact them and they'll explain everything involved. Not a major deal. BTW, I've even got a spare TH400 in the garage I picked up for $75 and put new stuff in just because it was cheap and short shaft. I'm sure if you talk to the folks at 4xHeaven you'll find out exactly what to look for too. Good luck and let me know if I can be of any further help. Gary
     
  5. SF87K5

    SF87K5 1/2 ton status

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    Thanks for all your help. I will let my buddy know what you guys have said.
     

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