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Difference in '87 14 bolt ff and newer model

Discussion in 'The Garage' started by jstevenj, May 16, 2005.

  1. jstevenj

    jstevenj Registered Member

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    Can someone give me the low down on the difference in the pre 87 14 bolt ff rear and the newer models. Everyone who sells disc brake kits says they work on 87 and older but what is different?
     
  2. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    The 87 and newer pumpkins are different designs, they are internally the same but externally the newer ones have tons of ribs, where the old ones are smooth. The reason the disc brake conversions won't work is that they changed the hub/brake design also. On the older axles, the hubs and drums are held together by the wheel studs. To do the conversion, you press the studs out, take the drum off, replace it with a disc rotor, and put new studs in. On the newer ones, they are two seperate pieces, and I believe you can take the drum off without messing with the hub. I think (don't quote me on this) that if you had a newer axle, all you would need to do the conversion would be a set of the old style hubs, which I imagine wouldn't be difficult to come by.
     
  3. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    The only internal difference I've seen is the inner pinion bearing on the finned housings (I think it was bigger).

    As for the brake drum thing, I have always heard the same thing Mikey_D05 posted - until I bought my crew cab. While I do have the late model finned housing, my drums are set up the same as an early 14 bolt (held together by the studs). Ratzila's brother had an 89 V3500 with a similar rear axle.

    My theory on the pull off drums is that they came in the 88+ C/K series trucks and that all of the carryover R/V series had the old style stuff (on the later housing). I have not proven my theory by installing an early rear disc kit on my truck but I can't see any differences in the brakes between my 76 & 91 14 bolts.

    Sorry, I know I just added a huge gray area to your question. :wink1:
     
  4. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    Haha, I was trying not to confuse him on the year variations. There are a few mixes out there (like mine), but it's easy enough to tell which style you have. If you get confused, just post a picture and we'll help you out.
     
  5. rdn2blazer

    rdn2blazer 1 ton status Premium Member

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    i have 2 early 14ff axles and a 89' crew cab with the finned center section, the hubs are the same on both,you have to press the studs out to get the drums off. so the disc conversions, im pretty sure should work on those late model 14ff too. i was told one time by a guy at offroad unlimited that the late model 14ff was not as strong as the early 14ff cause it was made from gray cast iron, not ductile cast iron. then added fins for aditional strength. i do know that grey cast is softer to machine and not weldable like ductile cast iron.
     
  6. u2slow

    u2slow 1/2 ton status

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    No. The new hubs aren't machined flat on the backside when they have the slide-off drum. You could swap hubs and make it work though.

    The slide-off drum starts in '92 on 1-ton SRWs, and 2500 Burbs w/BB or diesel. However, a 2500 pickup with BB or diesel still has the conventional back-mounted drums with the 14FF. :confused:
     

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