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Old 03-20-2009, 08:15 PM   #1
Troy Fab
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Default 1971 Triumph Tranny Plunger Mod.

I was going to PM this to one of the members here and thought I would post just incase anyone else runs into this and is to cheap to have the pros do it:

Just when I think I have things under control ...I find out 71 Triumph has a crappy leaf spring cam lobe selector. I need to modify to a Plunger Style. $100.00 to have the mod (they have a jig) done...dooogh. Being as cheap as I am and figuring I could do this myself I proceeding to staring at it and trying to figure out how to do this by making my own jig. The cam plate is mounted at an angle (/) and that is what makes it difficult.

I drilled a 1/4" hole in some 1" stock (alum) and faced both ends off. I wrapped a piece of electrical tape around to make up the .030 size differance. Then put a hose clamp on it and tapped it up against the boss. This gave me the right angle, I checked it every way I could imagine. I put a light under to make sure it was flat, good call cause I did see light after I tightend it up . I tapped till there was no light and drilled the 1/4" pilot hole. Checked with a transfer punch and it was dead on I made another jig and went though 3/8".

Now I need someone to verify the thread size of the plunger so I can drill to tap size. I will make a new jig for this. I do not have a plunger to verify size so if anyone knows for sure let me know. I also need to counter bore this hole for the plunger, I will cross that bridge when I get there.





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Old 03-20-2009, 08:30 PM   #2
Hartz Bros
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Default Re: 1971 Triumph Tranny Plunger Mod.

You will need a 5/8 18 tap, an 11/16 drill for the countersink, and a 37/64 drill for the main hole... And make sure the mounting/gasket surface on the bottom of the boss is completely flat or it will leak, no matter what.... The article in the May 07 Horse issure is great...
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Old 03-20-2009, 09:50 PM   #3
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Default Re: 1971 Triumph Tranny Plunger Mod.

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You will need a 5/8 18 tap, an 11/16 drill for the countersink, and a 37/64 drill for the main hole... And make sure the mounting/gasket surface on the bottom of the boss is completely flat or it will leak, no matter what.... The article in the May 07 Horse issure is great...
Thanks, I read the artical but wanted to make sure of the sizes just in case he threw those sizes out from memory when he wrote the artical.
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Old 04-26-2009, 10:29 PM   #4
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Default Re: 1971 Triumph Tranny Plunger Mod.

I forgot to put fore closer to this thread. Here is what happened after I got my plunger in the mail.

Now I could measure how much to counter sink, turns out 5/8" would be just enough. I decided to use a step drill figuring the taper would not hit the existing threads:

I drilled and then ran the tap thru backwards from the inside to clear the threads I might have messed up with the step drill:

I have heard if the boss is not flat where it seats these will leak. I put it in finger tight and checked with a feeler gauge. There was a .002 gap on one side:

I machined a slug with a hole to match the shaft of the tap and used double sided sticky tape to hold on some DA sand paper. I put black marker on the boss, screwed in the tap, slid the jig slug over the shaft of the tap and hand spun it until all the black marker was gone:



Done and ready to install tranny gears: It lines up perfect!
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Old 04-27-2009, 12:56 AM   #5
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Default Re: 1971 Triumph Tranny Plunger Mod.

Awesome!!! Yeah those leaf springs are a bitch (just ask Billdozer....) The plunger is the only way to go!

Andy
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Old 04-27-2009, 09:56 AM   #6
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Default Re: 1971 Triumph Tranny Plunger Mod.

"Quote" The plunger is the only way to go!


Yeah, I was warned not to try and use the leaf spring.
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Old 04-27-2009, 10:10 AM   #7
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Default Re: 1971 Triumph Tranny Plunger Mod.

Plunger mods are gay.

Oh, wait...no, that's actually cool. My bad.

I saw "tranny" and "plunger" & didn't know what I'd find.

Last edited by Dr. Benway; 04-27-2009 at 10:14 AM.
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Old 04-27-2009, 10:34 AM   #8
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Default Re: 1971 Triumph Tranny Plunger Mod.

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Originally Posted by Troy Fab View Post

Just when I think I have things under control ...I find out 71 Triumph has a crappy leaf spring cam lobe selector. I need to modify to a Plunger Style. .
What year did Triumph move away from the leaf spring and over to the plunger style?
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Old 04-27-2009, 11:27 AM   #9
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Default Re: 1971 Triumph Tranny Plunger Mod.

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Originally Posted by CLASSIC CYCLES INC. View Post
Awesome!!! Yeah those leaf springs are a bitch (just ask Billdozer....) The plunger is the only way to go!

Andy
No, please don't ask me about that particular device! Nice work, thanks for posting the how-to.
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