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hydro clutch in a 79

Discussion in 'The Garage' started by 79diesel, Apr 16, 2007.

  1. 79diesel

    79diesel Registered Member

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    I am putting a nv4500 into a 79 gmc sierra. It is replacing a th400. Does anyone have pictures or measurement of the location of the master cylinder in the 73-80 firewall? If not is it very hard to figure out? I dont want to be breaking pushrods.
    thanks
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Pretty easy to figure out! Bolt the hydro pedals in, then push the little support rods up against the firewall on the inside and drill the holes out.

    Next, find a piece of cardboard, put a hole in the center for the pushrod, then trim it to make it the same shape / size as the master cylinder, put the peice of cardboard on your firewall, put bolts through the two holes you drilled earlier, then use a hole saw to drill out the center hole.

    Bolt the master on, and you're good to go!
     
  3. 79diesel

    79diesel Registered Member

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    so should the cluth pushrod sit level when the clutch is disengaged?
     
  4. sweetk30

    sweetk30 professional hooker Premium Member

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    what nv4500 year and bell housing are you using? as the 96 - up internal hydro throwout bearing style take a diffrent line. and the 95 - down use pass side external slave that will mod easy to your old 85-91 old body style master. but the pass side slave might give drive shaft problems.

    and the way the 85 - 91 master bolts on is diffrent than 88-up new bodys.
     
  5. sweetk30

    sweetk30 professional hooker Premium Member

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    to install like he said. if you use a 85 - 91 pedel assembly its easy. bolt it in and remove the 2 studs and spacers. then mark the holes on the support rods and drill out. this will be the bolt pattern you need for the master. then just punch the big center hole in the propor place with a simple hand made templete and use the 2 mounting holes as a line up gide.

    thats basicly all i did for mine. but i had a 87 cab so the dimples were there. but real hard to see under the under coating.
     
  6. 79diesel

    79diesel Registered Member

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    I am using a 98 dodge nv4500. I am doing a 6bt cummins swap. This is a 2wd truck so driveshaft clearance wont be an issue. (yes i know this isnt the place for a 2wd but you guys seem to be the only ones that know anything about this stuff lol)
    So i will have issues modifying the line new style line to the gm master?
     
  7. Randy92782

    Randy92782 1 ton status

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    well i'm currently lookin into this myself. while lookin at my friend truck (87) it looked easy enough. but lookin at mine (79) where the clutch rod comes through next to the fuse box it has a lone set of wires. don't know if yours is like this but looked as though the wires might be in the way. idk just a thought
     
  8. 79diesel

    79diesel Registered Member

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    well it does look like it could be close to the fuse box but other then that there doesnt seem to be anything in the way that couldnt easily be repositioned.
     
  9. Randy92782

    Randy92782 1 ton status

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    oh well i just had bout 5 wires coming out between the fuse box and something else. they had it sealed with something. they may have just routed them themselves. thanks though
     
  10. 79diesel

    79diesel Registered Member

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    oh yeah i think i know the ones...if they are, they are mounted by the steering column plate and if you undo the holder you can move them out of the way.
     
  11. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    here is the measurments i took off a 85 k5 with factory hydro, been working in my truck just fine.
    [​IMG]
     
  12. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I used that map for my 81 Jimmy and it worked great. I swapped in an NV4500/203/205 and the hydro clutch stuff.

    Rene
     
  13. 79diesel

    79diesel Registered Member

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    awesome thanks
     
  14. 79diesel

    79diesel Registered Member

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    are the measurements the same for the 73-80 firewalls? i.e. does the wiper motor mount in the same location?
     
  15. supersize75k5

    supersize75k5 OrganDonorRacing.com

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    look in my pics on the supersize75k5 link in my sig below, there is some pics, one of which shows a aftermartket master in the factory spot, shows some detailed pics.
     
  16. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Yep, they are identical :)
     
  17. 79diesel

    79diesel Registered Member

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    alright thanks again
     
  18. Randy92782

    Randy92782 1 ton status

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    i'll try and take a pic and post it. hard to explain. i know the ones you're talkin bout though
     

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