Transmission & T-case options & availability - Ditching the 700r4

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Corey-88K5, Dec 24, 2000.

  1. Corey-88K5

    Corey-88K5 1/2 ton status

    Feb 17, 2000
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    Home: Michigan, Stationed: Hill AFB (Home of Moab.
    I'm going to do it. Screw the P.O.S 700. 3ed in 3 years is getting too expensive. I'm looking for options and requirements to mate a TH350/TH400 to a NP203/205. I'd like to go with a TH400 Non O/D to a TH205. What would I need, and what years would they be available? Parts needed. Would my NP208 mate to the TH400 for the time being?


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  2. Trying to find a TH400 and NP205 that are mated with crossmembers and shifters are like finding hens teeth. I have ran across 1 or two sets in three years of searching the web and a few salvage yards for them. You would likely need new shafts also. I think there is a 400/205 on the GM board on Off-road about a month or so ago that the guy wanted 350 for the pair. The only drawback was the NP205 was an 80 model with the slip yoke.

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  3. Here is his email I just found it.

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  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

    Jul 23, 2000
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    E-town baby!
    A TH 350/203 combo is easy to find, 73 to 79 K5's and others used this combo. A TH400/205 combo is another nice set-up that can be found in the one ton 4x4's. I think this combo was available into the mid 80's at least. With any of these swaps you'll probably need some driveshaft mods, and the shifter linkages may be a little fun. I'd try and get all the linkage stuff from the donor vehicle as well. I don't know if the 208 was ever mated to the TH400 though. I'm not 100% sure but I believe the 700R 4 has a 27 spline output like the TH350 and the TH 400 has a 32 pline output.
    Why not swap to the SM 465? Can't get much more bomb-proof than that, of course there's the fun of swapping pedal assemblies and all. Just think of the 6.54 to 1 first gear though! A lot of them came mated to the 208 too, it makes a killer combo for crawl ratio.[​IMG] 70 to 1 with 4.11's!



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