turbo 350m to turbo 400 swap

Discussion in 'Transmission & Driveline Topics' started by johnnycamaroz, Oct 1, 2018.

  1. johnnycamaroz

    johnnycamaroz Member

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    Does anyone know what needs to be changed, I think the yoke is all?
    I think the tras mount and cross member are the same?
     
  2. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    I beleive the you can use the same cross member, just move it back and drill two new holes. The driveshaft length will change also. Else should be good from what I understand. (haven't done it myself, just info from this forum)
     
  3. Evil Twin

    Evil Twin Veteran Member

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    When I did mine I cut the trans mount tab off the cross member and relocated it to the other side. The driveshaft was also a small issue even though I went from short shaft to short shaft. It was either a little to short or a little to long I cant remember but I think I had to have a little over an inch cut.
     
  4. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

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    when I replaced my BW super T-10 all I did was drill new holes for cross member and use original yoke and drive shaft.
     
  5. 74BIBELOT

    74BIBELOT Veteran Member

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    9C1C50E3-8764-4049-9080-757E58C547B4.png hope this helps:;
     
  6. INSPECTOR57

    INSPECTOR57 Veteran Member Lifetime Gold Member

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    The OP's car appears to be a '79, the early crossmember referenced above will not fit. You can use your existing crossmember & mount, there is room to slide it to the rear & drill new holes. The TH350 yoke will need to be changed & most likely the driveshaft will need to be shortened ~1". If you had the factory 4 speed you would have the correct yoke (as mentioned previously).

    Photo below shows differences - all on a '73 frame:
    Top - 70-74 TH400 only
    Middle - 70-74 all other trans
    Bottom - 75-81 All - note the overall length; about 1.25" more

    Crossmembers001.jpg
    crossmemberdata.jpg
    Transmission_ID_zpsp4jxqjoa.jpg


    Gary
     
    Last edited: Oct 1, 2018
  7. INSPECTOR57

    INSPECTOR57 Veteran Member Lifetime Gold Member

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    Noticed that last pic is hard to read the details
    Trans details.jpg
     
  8. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    instead of trying to drill new holes.... really a PITA.. unless the frame is laying on the floor....with NO BODY...
    Since GM did NOT see fit to offer a th400 in the late 2nds...... grab you an EXTRA th350 cross member.....simply cutt-off the shelf (gently)...re weld it onto the REAR of the cross member (facing rear of car) this will give you the 6" you need.
    NOTE!!!!! it is NOT CENTERED nor should it be.

    NO you can't use an EARLY 2nd gen th350 cross memeber turned around...(looks like it....but NOPE) What you make will LOOK like this turned around backward.


     
  9. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    NOTE: the difference in appearance is due to the EARLY model frame crossmemeber mounting holes are FURTHER toward the rear of the car!!! Last note... really.... also notice the mounting holes.. DRIVER SIDE holes are SLOTS!!!! due to not on center...;)
     
  10. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    crossmember mounting location[​IMG]
    left side shows is 70-74...................................right side is 75-81
     

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