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converting SF rear from 8 to 6

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by K5Chris, Jul 9, 2004.

  1. K5Chris

    K5Chris 1/2 ton status

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    how difficult would it be to convert a 14 bolt sf from 8 lug to 6 lug? is it just new axle shafts and brakes? how much would a set of 6 lug shafts run?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm listening. /forums/images/graemlins/smile.gif

    I too have contemplated doing this. There doesn't seem to be much info out there about these axles though...did spline count ever change? Is the axle housing brake flange all the same? Are they still being used by GM? (I have yet to see a 14SF in a 2000+ truck FWIW, all I seem to see are 1/2 tons)

    My idea was/is to use a 2000+ SF axle, so that I could go with the disk brakes off the same vehicle. But, if you could swap the newer brakes to the older axle, or older axleshafts into the newer housing, the 6 lug/8 lug issue wouldn't matter.
     
  3. Blue85

    Blue85 Troll Premium Member

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    I did this. I used an 8-lug axle from an 80-something Suburban, which had the right spring and shock spacing. I bought new axleshafts for about $90/each. Every axle I have seen or heard of is 33-spline. The lengths of the shafts did vary based on the size of the brakes, which is the tricky part. All of the shafts will fit in all of the housings, as the seal and bearing surfaces are in the same place. I actually could only find one length of 6-lug shaft, but I don't know what is available in junkyards. Fortunately, this put my rear track width very close to the front track width.

    Normally, I assume you would just need 6-lug drums and that would be all. In my case, I built disc brakes before swapping the axle under the truck. The drums are like $80/each, so this was a good alternative. A mid-90's Chevy 4x4 front rotor fits perfectly on the flange of the 6-lug shaft, so no machining was required. I used 80's front calipers and 80's front backing plates. I ended up needing 1.5" spacers between the backing plate and the brake mounting flange on the axle tube. This is the part that could vary based on axle-shaft length. The only custom fab was to make the spacers and to machine out the holes in the backing plate (bolt pattern is different and axle tube size is larger.) All wear items are standard cheap parts.
     
  4. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    My donor axle was an 82 14bsf from a diesel. There are two different sets of 6-lug 3/4 ton axles shafts. You want the longer ones. They will make the track width really close to the front. The 6-lugaxle shaft rides on the same bearing surface as the old 8-lug shaft. I decided to go with drum brakes for e-brake reasons. This is where I ran into problems. The old brake mounting flange needed to be cut off and reweld for the backing plate and drum assembly to line up and function properly.

    The drum brakes are the same diameter as your 10-bolt brakes, I believe 11" so 15" wheels will fit over them without any problems. I got all the brake hardware, drums and backing plates from a 94 Z-71. Just make sure you tell the parts guys or junkyard people it has the 6-lug 14bsf rear end. I found it easier just to go around the local junkyards and look because most of the time they didn't know there was an option for a 6-lug 14bsf.
     
  5. K5Chris

    K5Chris 1/2 ton status

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    [ QUOTE ]
    I'm listening. /forums/images/graemlins/smile.gif

    I too have contemplated doing this. There doesn't seem to be much info out there about these axles though...did spline count ever change? Is the axle housing brake flange all the same? Are they still being used by GM? (I have yet to see a 14SF in a 2000+ truck FWIW, all I seem to see are 1/2 tons)

    My idea was/is to use a 2000+ SF axle, so that I could go with the disk brakes off the same vehicle. But, if you could swap the newer brakes to the older axle, or older axleshafts into the newer housing, the 6 lug/8 lug issue wouldn't matter.

    [/ QUOTE ]

    i contemplated the same thing for my 14bFF...... BUT, the '99+ brakes require a 16"+ wheel. i dont wanna run bigger than 15. GM DOES still use the 8 lug 14bSF on light duty 3/4 tons. the H2 has it, as well as 1500HD's, and non-HD 2500's. i don't think they still put the 6 lug in half tons anymore. that was only in 88-98 IIRC.
     
  6. K5Chris

    K5Chris 1/2 ton status

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    thanks for the info guys /forums/images/graemlins/peace.gif

    this is not actually for my K5..... i'm building a FF in the garage.
    this is for my friends '96 Z71. there is no way to convert his IFS to 8 lug, and something has to be done about his 10 bolt rear.

    my 10 bolt rear actually has a disc setup, that i might be able to use on the SF 14.... it uses '89 K1500 IFS light duty front rotors with the center hole cut to fit over the axle flange. and, it uses '86 Mustang SVO rear calipers & caliper mounting brackets w/ ebrake. i also have 2 sets of '91 half ton SFA front rotors that could be used.

    where do i get the axle shafts? is this a junkyard search item? or, does any aftermarket company make them? if i gotta search junkyards for axle shafts, i might as well try to find a whole 6 lug axle.
     
  7. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    thanks for the info guys /forums/images/graemlins/peace.gif

    this is not actually for my K5..... i'm building a FF in the garage.
    this is for my friends '96 Z71. there is no way to convert his IFS to 8 lug, and something has to be done about his 10 bolt rear.

    my 10 bolt rear actually has a disc setup, that i might be able to use on the SF 14.... it uses '89 K1500 IFS light duty front rotors with the center hole cut to fit over the axle flange. and, it uses '86 Mustang SVO rear calipers & caliper mounting brackets w/ ebrake. i also have 2 sets of '91 half ton SFA front rotors that could be used.

    where do i get the axle shafts? is this a junkyard search item? or, does any aftermarket company make them? if i gotta search junkyards for axle shafts, i might as well try to find a whole 6 lug axle.

    [/ QUOTE ]

    I am sure all companies that sell axle shafts will have that axle, I don't know how much it would be.
    I know moser has them for $150 and that is actually better than stock but I think not the Chromoly.
    Check with all the aftermarket companies that sell shafts.
    /forums/images/graemlins/waytogo.gif
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    BUT, the '99+ brakes require a 16"+ wheel.

    [/ QUOTE ]

    Is it because of the rotor diameter and thus the caliper sticking out too far? I know on the new Astros the rear disks are 13", I doubt that setup would fit behind a 15" wheel either. Just a 12" rotor itself should fit no problem though if I remember right. Hmm.
     
  9. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    Why doesn't he just find one from the 88-98 generations. My buddy has a 92 light 3/4 and it has a 6 lug 14 SF I also believe the 1/2 tons with tow package got them. /forums/images/graemlins/waytogo.gif
     
  10. Blue85

    Blue85 Troll Premium Member

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    If you get the newer 6-lug version it only requires relocating the spring pads and shock mounts.
     
  11. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    [ QUOTE ]
    Why doesn't he just find one from the 88-98 generations. My buddy has a 92 light 3/4 and it has a 6 lug 14 SF I also believe the 1/2 tons with tow package got them

    [/ QUOTE ]
    May be a dumb question, but does everything look the same, just that it has 6 lugs vice 8?
     
  12. clarkjw24

    clarkjw24 1/2 ton status GMOTM Winner

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    Try this link for pricing on axle shafts. Hill 4wdr
     
  13. afroman006

    afroman006 1/2 ton status

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    [ QUOTE ]
    Why doesn't he just find one from the 88-98 generations. My buddy has a 92 light 3/4 and it has a 6 lug 14 SF I also believe the 1/2 tons with tow package got them.

    [/ QUOTE ]

    Because he's buying the axle from me /forums/images/graemlins/shame.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/waytogo.gif
     

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