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T90 Synchro Hub

Discussion in 'Flat Fender Tech' started by Downs, Sep 21, 2022.

  1. Sep 21, 2022
    Downs

    Downs Rattlecan All The Things!

    Hunt County Texas
    Joined:
    Jul 25, 2020
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    579
    Got the last of the parts in today to finish the overhaul of my T90. When test fitting the blocking rings into the new synchro hub, they are way too tight, so tight they won't go all the way into the hub and don't have any rotation. Even the old, worn blocking rings won't fit inside the hub properly. I'm guessing the new hub is just a couple of thousandths too tight, I'll see if I can get my micrometer on it in a bit and see just by how much. No one state side had these assemblies in stock, so I ordered over eBay from India. My old synchro hub seems to be in decent shape, but the sliding clutch is eaten up with rust and the blocking rings were worn out, along with the dogs having 2 of the 3 missing end pieces.

    Right now my plan is to put reuse the old hub with the new sliding clutch, dogs, springs, and blocking rings. Another option is to take it into one of the local machine shops and see if they can open the ID of the hub to match the old one.

    As it stands, that will leave only the synchro hub as a used part in the entire transmission, with exception to the case itself. Everything else will be NOS or from Herm.

    Does anyone see any issue re-using the old synchro hub? It still fits tight on the NOS mainshaft I got and seems to fit the sliding clutch very well too.

    Thanks,
    Josh
     
  2. Sep 21, 2022
    Downs

    Downs Rattlecan All The Things!

    Hunt County Texas
    Joined:
    Jul 25, 2020
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    NEW HUB= 2.2615

    OLD HUB= 2.2520

    This is the measurement I got on the inside surface of the synchro hub where the blocking rings ride.
     
  3. Sep 21, 2022
    fyrmn

    fyrmn Member 2023 Sponsor 2022 Sponsor

    High Desert AZ
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    Did you try Pete Debella? He had some nos a while back
     
  4. Sep 22, 2022
    Downs

    Downs Rattlecan All The Things!

    Hunt County Texas
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    I did not. I've never heard of him.
     
  5. Sep 22, 2022
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
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  6. Sep 22, 2022
    fyrmn

    fyrmn Member 2023 Sponsor 2022 Sponsor

    High Desert AZ
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  7. Sep 22, 2022
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    That hub really doesn’t get much opportunity to wear. If the hub is not damaged, I would not hesitate to re-use it in the rebuild.
    -Donny
     
    Downs likes this.
  8. Sep 23, 2022
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Sep 23, 2002
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    12,529
    Depends. I’ve seen plenty of hubs where the splines the clutch sleeve slide on we’re worn partially causing the sleeve to hang up. Plenty of them with the hub splines where they were sloppy on the main shaft too. However, I’ve seen plenty that were virtually pristine also. My recommendation is to inspect the hub very closely and if it appears ok with no wear or roughness on the splines then Put it together then operate it by hand hand and make sure there is no play and absolutely no binding whatsoever. If not then will “probably” be ok. I’ve done it with success but the industry standard is to not mix and match the sleeve and hub. Also industry standard to mark the sleeve and hub to reassemble in the same rotational position because of the wear patterns that develop. And yes, they do develop and if not assembled correctly can cause binding. Even today some manufacturers hand fit the clutch sleeve and hub for some applications. Back in The day it was even more common. Commonly it’s cost effective to purchase a synchronizer assembly that comes with an assembled synchronizer assembly with blocking rings. All new parts that are matched.
     
  9. Sep 24, 2022
    Downs

    Downs Rattlecan All The Things!

    Hunt County Texas
    Joined:
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    Yeah, I did that, but the Synchro assembly I got in from India was 9 thousandths too small, and the new blocking rings wouldn't fit.
     
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