2.5" v.s. 3" drum brake difference

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Vern, Aug 10, 2018.

  1. Vern

    Vern Registered User

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    Hi there, can anyone help me out by explaining the differences between 2.3 and 3 inch drum brakes before I get in there this evening? Obviously the drum and shoes are different but what about hardware and backing plate?
    Bought 3" shoes when i need 2.5 but the parts truxk has 3 and drums look good. Perhaps there's some parts compatability.
    Thanks in advance.
     
  2. towcat

    towcat Administrator Staff Member

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    2.5" SRW
    3" DRW
     
  3. hce

    hce So can i.... Supporting Member

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    2.5" below 8500 gvw
    3" above 8500 gvw
    3.5" is for duallies.
     
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  4. ifrythings

    ifrythings Full Access Member

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    You mean
    2.5” semi floating
    3.0” full floating srw
    3.5” full floating drw
     
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  5. Vern

    Vern Registered User

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    Apparently there are 3" on my parts truck srw with overload springs also. I'm wondering what needs swapping to upgrade to the 3".
     
  6. hce

    hce So can i.... Supporting Member

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    I would imagine the only practical way would be to swap rearends.
     
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  7. Vern

    Vern Registered User

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    You don't think the backing plates could be removed then?
     
  8. Vern

    Vern Registered User

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    o.k. I see the full floater wasn't offered with 2.5" brakes, and in my particular case somewhere along the line a PO put 2.5" shoes in a 3" drum. The 2.5" drum I bought would not fit over the axle flange. What a saga.
     
  9. Dirtleg

    Dirtleg Full Access Member

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    Just to muddy it up some more. When replacing my rear wheel cylinders I was able to determine the F250, F350 SRW and F350 DRW wheel cylinders were all different.
     
  10. Macrobb

    Macrobb Full Access Member

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    Just curious, but did Ford ever put a semi-floating 10.25 behind an IDI? I've only seen full-floating 10.25s and Danas on the earlier models.
     
  11. compressionignitionrules

    compressionignitionrules Full Access Member

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    I had a dana 70 behind an idi, but it was a 1984 F250 with a T19 . never seen a Fseries semifloat behind anything but a 4.9 or 5.0 in a an F250 light duty.
     
  12. subway

    subway be nice to the admin :D

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    i had a semifloat in my F350 crew but i think that was swapped in, i was under the impression that the semi floats were only a light F250 option.
     

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