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Thread: such strange thread on gear shift knob

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  1. #1
    Luke Skywalker
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    such strange thread on gear shift knob

    I helped a friend get a new shift knob to fit. I have the taps for the project. I was surprised that the size of tap was 7/16 32. That is a very odd tap. Why would Triumph use a tap that probably is not used anywhere else on the car? Perhaps the transmission came from another company and they decided to use that thread count?

    Jerry

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    Yoda martx-5's Avatar
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    Re: such strange thread on gear shift knob

    Yes, not a common size, however, my local machine shop supplier had both the tap and die in stock. I needed to chase the threads on the lever arm as they were messed up quite a bit. The die was too costly, so I wound up using my tread file. More work, but no outlay of money.
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Yoda PeterK's Avatar
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    Re: such strange thread on gear shift knob

    Looking for a 7/16-32 jam nut if anyone knows of a source.

    I tried ultra thin electronics nuts that fit but they're too thin and don't hold.
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Yoda martx-5's Avatar
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    Re: such strange thread on gear shift knob

    The parts book for the TR3 doesn't show that any jam nut was ever supplied. I just screwed the knob all the way down and the shift diagram pretty much lined up. That may be one of the reasons for the fine threads. You can get it tight enough and still be close to having the diagram straight.
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Jedi Hopeful
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    Re: such strange thread on gear shift knob

    Mine definitely has the nut. Tried to identify the thread but no record of that pitch and diameter in my tables. My guess on the fine thread is that it is similar to the brass threads, allowing threading of thin walled tubes.

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    Yoda PeterK's Avatar
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    Re: such strange thread on gear shift knob

    I have a tap and thought I'd try to reithread a 7/16-20 jam nut. I think the originals (or Amco) are chrome.

    I don't mind the pattern not lining up but hate driving with a loose shift knob under hand..
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Great Pumpkin TR3driver's Avatar
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    Re: such strange thread on gear shift knob

    Quote Originally Posted by martx-5 View Post
    The parts book for the TR3 doesn't show that any jam nut was ever supplied.
    A minor misprint IMO. After 2877, the shift lever was one piece, hence no need for the "nut, locking lever in ball-end". 109047 is actually the nut locking the threaded knob (introduced at the same time).


    I found it listed for sale at TRF, Rimmers and Revington, didn't look at others.

    I've tried the "screw it down until it's tight" approach, didn't like the results. Kept coming loose at times when I really didn't want to be focusing on my shift knob! And it eventually broke my nice aftermarket walnut knob.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: such strange thread on gear shift knob

    Quote Originally Posted by PeterK View Post
    Looking for a 7/16-32 jam nut if anyone knows of a source.

    I tried ultra thin electronics nuts that fit but they're too thin and don't hold.
    Try Macy's Garage:
    https://macysgarage.com/parts-hardware.htm

    Towards the bottom of the page.
    Keith

    1957 TR3 TS20447LO (2017-)
    1962 TR3B TCF1183L (1979-1982)
    1966 Spitfire MKII (1972-1975)

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    Jedi Trainee Graham H's Avatar
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    Re: such strange thread on gear shift knob

    Yes Keith, I got one from Macy's had to do some fast talking to get them to send it to Australia without charging silly money for shipping. At the time it was the only one i could find World wide.

    Graham
    [SIGPIC][/SIGPIC]

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    Yoda PeterK's Avatar
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    Re: such strange thread on gear shift knob

    Thanks Keith but $16.95 + shipping is crazy $ (I realize that they have to recoup their labor producing them) and I have a brass nut that I can re-drill and tap so I think that I'll go that route. The tap cost was less. Thank you!
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Great Pumpkin TR3driver's Avatar
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    Re: such strange thread on gear shift knob

    TRF only wants $5.95. I'm not certain, but I think originals were chromed steel rather than brass, so probably the one from TRF is, too.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

  12. #12
    Yoda PeterK's Avatar
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    Re: such strange thread on gear shift knob

    Brass is because it's easy for me to thread, and I have one to use.
    PeterK
    1958 TR3A 1966 TR4A both HVDA

  13. #13
    Luke Skywalker
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    Re: such strange thread on gear shift knob

    The replacement knob I just threaded has a plastic insert. I think he bought it from Rimmer. You have to drill and tap it yourself. I am hoping it will be nice and tight, I threaded about an inch of it to screw on.
    Jerry

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