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ZF5 reverse - repair time!

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Macrobb, Nov 18, 2019.

  1. Macrobb

    Macrobb Full Access Member

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    I'm playing around with a '93 ZF S5-42 which... won't go into reverse. Just plain grinds.
    However... If I pull the shifter off the top, and manually stick it into gear using a couple of screwdrivers to lever the "socket" piece... it'll go and stay in reverse.
    It's like it won't go quite far enough with the shift lever. All other gears work fine.

    Any ideas on what might be worn out or missing to cause this?

    (Note: I've got no history on this trans. It was found in a JY on top of a stack of junk, missing the shifter. Got it really cheap because of that).
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Bent shift fork I bet.
     
  3. Shamoke

    Shamoke Registered User

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    Sloppy linkage?
     
  4. ifrythings

    ifrythings Full Access Member

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    Sounds like your blocker ring is wore out and the synchro sleeve and gear are wore down.

    I had the problem of sometimes grinding going into reverse and popping out of reverse.

    I replaced the 5-R synco assembly and reverse gear to fix it.

    Old reverse gear with blocker ring
    A65F276F-5B66-47A6-ABCD-30CA3F57EB2E.jpeg

    Old reverse gear with ground down teeth
    B4E43ABB-1782-4647-B667-58DA21388E0E.jpeg

    Old 5-R synchro slider showing the ground down teeth on the reverse side
    9164420D-B662-4400-80D2-83D0DC3601B6.jpeg

    New reverse gear
    18EA0F93-ADCF-4A45-9E47-1E53FBFF1528.jpeg

    New 5-R synchro slide
    FE595761-A93E-48A3-9C8C-EBD76651B308.jpeg
     
  5. BlackNoma

    BlackNoma Full Access Member

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    mine grinds going into reverse unless I put it into a gear first and then go to reverse. or if it's the first gear I put it in after I start the truck. kinda weird, but no big deal.
    keep us updated on what you do to fix it.
     
  6. hesutton

    hesutton The Anti-Anderson Supporting Member

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    I had the same issue as pictured above on 460 ZF5 I swapped into the 6.9 crew cab. Had to replace the 5/R synchro and slider. No issues since.

    Heath
     
  7. Macrobb

    Macrobb Full Access Member

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    So... good and bad news. First off, I ended up taking the shifter and machining a small chamfer on the copper ring where it would limit the travel of the shifter lever itself. This got me a few extra thou of shifter 'throw'... Didn't work.
    Then I pulled the top off(that piece just under the shifter, where the 5th/reverse lockout is), and ground off just a bit of the round 'bit' on the upper left, which the 5/r lockout slider piece normally is - again, to allow the shifter to go just a hair further forward.
    This... worked! Somewhat... it's still janky. But it did go into reverse.
    We took a test drive, and aside from something inside the trans(probably the 5/r slider) bouncing back and forth and knocking off something... it did drive.
    However, it's coming apart, obviously. All the synchros are pretty toasted, too...
     
  8. Randy Bush

    Randy Bush Full Access Member

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    Kiwif150, riphip and Macrobb like this.
  9. typ4

    typ4 Supporting Member Supporting Member

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    Replace the roll pins that hold the forks to the shaft while it's apart. Don't ask, lol
     
    Selahdoor, riphip and chillman88 like this.
  10. Chuckmeister

    Chuckmeister Registered User

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    All of the above. My '89 F 250 has had that problem since I bought it and I have been keeping my fingers crossed. Once it's in, its in. Most of the time I can keep it from grinding by"popping" it into reverse. The momentum seems to carry it beyond the slop or wear. Putting it in an other gear first seems to help too. Gets the gears stopped so nothing slows up the momentum of shifting. I know I'm going to have to deal with it eventually, but I haven't seen it get worse over the 5 years I have had it. Hope this helps someone like me who just wants to have a usable work truck.
     
  11. Nathan Uskoski

    Nathan Uskoski Registered User

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    Can you please bench test the transmission after rebuilding it. I just finished one and though I may as well bench test it. It shifts great but there is a clicking or popping noise. I took it apart and reshimmed the counter shaft. It is noisy and I am not sure what it is excepted.
     
  12. Macrobb

    Macrobb Full Access Member

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    I'll let you guys know if/when we do something with the trans - for now, we found an '87-91 460 zf5 in a JY last weekend for $100, pulled that, drilled it out and dropped it in earlier today(My friend and I can now pull and replace a ZF5 in an OBS in about 3 hours... getting faster at it!).

    Found a little glitch - the '97 PSD we put this trans in has a SMF, and the very edge of the pressure plate interfered with the little support rib on the inside of the bellhousing... by about .010". We figured this out by the horrible clicking noise on first startup. I decided to just run it and call it good, and it 'self-machined' some relief within a couple of minutes, and runs great now!
     

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