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engine /tranny swap please help

Discussion in 'GM Powertrain' started by rixjohnson, May 21, 2010.

  1. rixjohnson

    rixjohnson New Member

    whats up guys i can sure use some advice right now,so any and all help is appreciated im workin on my 1981 gmc sierra grande 2500,when i bought the truck it had a 350 and th350 tranny.im buildin it for as a daily driver and as my tow vehicle so i went with a 454 bbc and a th400 tranny ,so everything is gettin changed and thats where i need the help guys .first the engine what needs to be done to mount it any electrical need to be installed changed etc ,oh yeah the 454 is a 1985.how about the tranny what needs to be done the one that came out had the 9"piece on the end and i have a 2 piece driveshaft ,the new tranny needs to be ordered ,the engine is being rebuilt as we speak all replies appreciated :great:
  2. ejohnson03

    ejohnson03 Epic Member 5+ Years 1000 Posts

    If you are going from a 350 carb. to a 454 carb. motor there should not be any Electrical changes.

    Might need a heavy duty starter...

    Motor mounts are different between a SBC and BBC.
  3. rixjohnson

    rixjohnson New Member

    thanx do you know anything bout the transmission
  4. rustyk2

    rustyk2 Rockstar 4 Years 500 Posts

    Transmission should bolt right in. the cross member might need adjusting, not sure, but its pretty strait forward. My 88 suburban has a 350 sb and a th400 tranny. there are a bunch of different setups that will work. Also there is plenty of room under the hood. Motor mounts will need to be changed, the frame mounts will be put on the lower holes , they should be pre-drilled. other than that pretty simple. I put a 400 BB pontiac in a 77 chevy truck. Had it done in one weekend.

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