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TH200r4 to TH350 Swap

Discussion in 'The Garage' started by imaginepro, May 20, 2006.

  1. imaginepro

    imaginepro Registered Member

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    Hey guys well I am going through the last project for awhile on my truck and hope you guys can help me out. I have an 86 Chevy K5 Blazer. It came with a 350 with a TH200r4 tranny witch had an NP208 on it. So I replaced the 350 with a new crate motor but didn't have the money at the time to do the tranny. So I used the Th200r4 with the NP208. So everything worked kind of fine for a while. But since I used the old tranny it eventual died. So now I am swapping it out. I got a TH350 from a friend of mine and also the NP208 with the adapter that was with it. So I took the NP208 off and went and got a brand new TH350. So Now I have this new TH350 with the NP208. So everything is fine there. But I notice that the mount to the cross member off the new NP208 is allot longer then the one that is on my old NP208 that is off the truck that has the adapter for the TH200r4. So buy my guess I am going to have to get a new cross member. So I was wondering if any one else has done this swap? And if so what did you have to do with the cross member? And if I need one dose any one have one laying around? Also the new TH305 I have has a hole for a Kick down cable and also has the Vacuum module on the back. Do I have to hook up both? Thanks guys I hope someone can help me
    :confused:
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    First let me start by saying you did not have a TH2004R you had a TH700R4. Now i'm not sure about the tall and short adapter if they're interchangeable or not but if they are the same width from the tranny to T-case you can just use the original adapter so you can reuse your existing crossmember. As far as the kickdown cable is concerned you do not have to hook it up but the hole does need to have something in it so it doesn't leak fluid all over the place. The vacuum modulator must be hooked up to manifold vacuum for the tranny to shift correctly.
     
  3. imaginepro

    imaginepro Registered Member

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    Actually I do think it is a 200r4 When I did a filter change on it before it died it the 200r4 was the only pan seal and filter that fit. So I think someone put it in before I got the truck. So it dose need to be hooked up to manifold vacum. Thank you for your help and I just need to put a plug in the cick down cable whole? As far as the t case I belive the shaft on the older tranny and T case is shorter then the one for this trans. So It would have to be the same size tail shaft to work with the old Tcase correct?
     
  4. sweetk30

    sweetk30 professional hooker Premium Member

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    200 was a non bolt on tail tranny no way you would get a tcase adaptor on the tranny.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    You can't bolt an adapter to a 2004R, so you don't have one.

    As long as the adapter *length* is the same, you will have no problem using either adapter, just get one of the "humped" crossmembers, both single and double hump crossmembers use the same tranny mount.
     
  6. imaginepro

    imaginepro Registered Member

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    Wow well I don't have a 200r4 that is good to know I wonder what I would have. It might be a 700r4. But When I did the filter That was the first one I tried and it didn't work. But thanks guys. As for a humped corssmember I have one. But with the mount on the hump it seems like it wouldn't fit. But sould I flip the hump so it gose down instead of up.
     
  7. surpip

    surpip 1 ton status

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    and going from a 700 to a th350 really doesn't do anything for you other than you loose a over drive, and have a taller first gear ratio
    the trannys are pretty close to the same strength wise
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    My mistake, you said '86, so it is the later crossmember. All the humped crossmembers use the same height adapter, so no, you don't need to flip it.

    Pre-'85 adapters are taller and use a different crossmember.
     
  9. wayne

    wayne 3/4 ton status

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    First off, you had a 700r4 like mentioned. The 200r4 was a car trans. Anyhow you need the correct crossmember to go with the adapter you will use. It should be pretty easy to find in a junkyard.
     
  10. imaginepro

    imaginepro Registered Member

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    Thanks for all your help guys. Good to know. The reason is not that I want to the other tanny is dead. And the 350 I already had. So I need a crossmember for the adapter witch I think is older then an 86. So if anyone has one? I would like to know
     

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