Super 10 trans grind downshift from 7/8

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by BronsonA14, Jan 12, 2025.

  1. BronsonA14

    BronsonA14 Bobtail Member

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    Bought a truck recently with super 10 transmission and it will grind when downshifting from the 7&8 hole. Drove another truck a while back that did the same so guessing this may be somewhat common on these. What are possible causes?
     
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  3. Stringb8n

    Stringb8n Road Train Member

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    Maybe the synchronizer on the tail of the transmission?
     
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  4. Judge

    Judge Road Train Member

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    Usually synchronizers as said.
    Sometimes you gotta change the range selector itself on the gear stick too,
     
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  5. AModelCat

    AModelCat Road Train Member

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    Is it the shift lever that is grinding when making that shift or does the lever shift fine into 5/6 and its grinding and trying to find a gear after the lever falls into 5/6?

    Those transmissions only have the one synchronizer do they not? (Super 10 essentially never existed where I live, nobody has one). If it were the synchro you'd think you'd see it clash on every shift that uses the synchro. Not saying it can't be the synchro, just seems odd it would only show up in one of the five downshifts involving the synchro.

    If its the lever that's grinding trying to drop into the 5/6 hole I would probably put my focus on the main box first instead of the aux.
     
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  6. BronsonA14

    BronsonA14 Bobtail Member

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    Mine does it after you drop it out of gear and move the lever to the left side of the neutral slot. Not sure exactly how they operate but I know when you’re sitting still and you move the lever side to side in neutral you can hear an air valve opening/closing so guessing that actuates a high/low mechanism
     
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  7. LOTSO

    LOTSO Medium Load Member

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    That's why they quit the Super 10. They were nothing but trouble. I had one and would always shift to neutral, flip the splitter, and then shift back to into the gear. Super 10's never split as smooth as a 13 speed.
     
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  8. rollin coal

    rollin coal Road Train Member

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    I drove trucks with super 10's for 5 or 6 years when I first started trucking and never had any of those problems. I liked them. They quit manufacturing them over 20 years ago probably his is a little worn.
     
  9. RockinChair

    RockinChair Road Train Member

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    That was the only way to make it shift between 9th and 10th. The one I drove had a tendency to shift between 9 and 10 (both ways) at too low RPM.
     
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  10. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    Also a fan. I saw one that went over 3 million miles with just a snychro change when we did the clutch. One owner truck though.

    Biggest issue with them, like most, drivers who didn't know how to shift them.
     
  11. rollin coal

    rollin coal Road Train Member

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    Yep that's exactly what I figured... They were actually a fairly common fleet spec transmission back then which is hard to imagine considering today's world.
     
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