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TR2/3/3A such strange thread on gear shift knob

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Jerry

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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
 
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.
 
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.
 
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.
 
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.
 
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..
 
martx-5 said:
The parts book for the TR3 doesn't show that any jam nut was ever supplied.
Click to expand...
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).
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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.
 
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
 
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!
 
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.
 
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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