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Tranny swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kchecca, Sep 30, 2001.

  1. kchecca

    kchecca Registered Member

    Joined:
    Sep 26, 2001
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    Location:
    Feeding Hills, MA
    Hi all. I am new to the list and to this whole Chevy thing. We are rebuilding grandpa's '77 Blazer. Body is looking OK now and I am starting to move on to the engine and the tranny.

    It's got a 350-4 barrel, a TH350 tranny, and an NP203 case. its all original (I think) and pretty tired. The engine I think will go for a while and I might just keep the case....but the tranny needs work soon. What do you folks think about these options?

    1. Replace the TH350 with lock-up 350? Is this an easy wiring job? It would buy me some better mileage with the strength of the 350.

    2. Swap to a 700R4? Should be a reasonable swap as far as ease. I might get an NP208 case with it and that would be OK. Dig the low first and OD. What are the pitfalls with that idea, spline count and output on the engine?

    3. I think I am going to rebuilt a 350 and drop it in as a direct swap. Nothing crazy, just some basic low end power for towing and general travel. Can I convert to TBI or other FI easily? Would it be bold on using later model stuff, or am I better off just keeping the carb. It could use a tune, but runs good now.

    Thanks for letting me ask all my questions.... this truck rules. I did the body to get it past inspection (and looks) and I plan on leaving it as a nice familty truck-ster for a while, then going large once the kids are big enough to get themselves into it. Thanks again.

    --------------------------
    Keith C
    Bigbird '00 Jeep TJ
    Grandpa's '77 Blazer
     
  2. reddog64

    reddog64 1/2 ton status

    Joined:
    Nov 9, 2000
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    Location:
    Federal Way, Washington
    If you never want to do any seriour off roading and want increased mileage go with the 700r4... it's known to have problems though especially when beaten off road... If you switch tranny's to this one... you will need an adapter for the np203 or a 208 to go with it... which means different driveshafts... I'd just drop in a new th350....
     

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