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Joined: Aug 2001
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Project 39-1/2 - I am sorting the best parts from 3 transmissions to make one good 4 speed transmission. The engine I'm building is a '72 five speed - the trans does not have the improved later gears, so I am building as a 4 speed. I have two 4 speed trannys - at least one is a 1968 trans in reasonably good condition. Can you give me a thumbs up or down on the condition of the following parts, please.
[Linked Image from i.postimg.cc]
Gear selector camplate - wear on both sides of track, more visible on the left side in photo.

[Linked Image from i.postimg.cc]
Camplate again - wear all around but worst is in this section.

[Linked Image from i.postimg.cc]
Kickstart springs - is one of these better than the others? In the photo I lined up the inner tangs facing the same way.
Thanks.
Al
Making progress with your help!

Last edited by Al Eckstadt; 11/06/22 10:28 pm.

Al Eckstadt
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The camplate looks OK, though the later hardened ones are much better.
The middle kickstart spring looks tired, the others are OK. Look for corrosion damage that may give rise to a fault. They do break sometimes.
Beware that sometime in the late 60's Triumph decided to make their transmissions according to the drawings, after which parts like shafts and gears wouldn't interchange with earlier versions. How strange is that? Something to look for, though I'm not sure when the change took place. 1970 perhaps. My memory isn't better than it used to be...

SR

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Do a search on "triumph 4-speed gearbox changes" and download Hermit's article - that will give you chapter and verse

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Thank you both very much SR and Tinkerer. I am being very careful about mixing (and/or not mixing) certain parts. The two 4 speed transmissions are very different. One came from a '68 Bonneville parts bike I bought many years ago, the other from a '68 engine purchased for this project. The one from the parts bike is very very different (older style) than the one from the engine only. So there is little opportunity to use any of those parts.. There is no guarantee that either is correct for 1968 but the engine only tranny seems to be correct.
The final engine choice has turned out to be '72 T120RV, but I don't care to use the 5 speed as I mentioned above. The engine is in pretty good shape overall, so I am using the '72 parts where possible. This is where I have to be careful - mixing '72 parts and '68 parts.
I have been making good use of Hermit's website - but I missed that article on the gearbox changes. The site has soooo much info it is sometimes a little overwhelming. I used the article this afternoon to sort out the parts I was using. I appear to be OK so far.
Thanks so very much.
Al


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Hi Al, Unless the '72 transmission has been converted to plunger cam plate indexing, you should use a leaf spring cam plate.

Mid season '70 the leaf spring was introduced. This changed to outer shape of cam plate to accommodate leaf spring. Factory brought plunger back in 1973 on 5 speed. I don't know on '73 4 speed. But... the point of plunger was changed to fit with leaf spring cam plate. So a new or good used leaf spring 4 speed cam plate should be used.

I know you can build the 4 speed at lower cost. But end of day, the 5 speed is a really well working transmission with a much better spread of gear ratios. If... you are going to keep bike & ride it, the extra cost of 5 speed parts are worth it in the long run. Ordering trans parts direct from UK right now with the dollar exchange rates is very, very desirable. You can save several hundred dollars over US sellers. Shocking the amount of savings.

In May of 2021 I ordered a lot of 5 speed parts from onestopbikebits on eBay. He has reputation online. However purchasing through eBay is very good as you have eBay protections. They do exchange rate & all that. If you are interested in quote, email him via eBay. YOU MUST!! be very accurate on exact part numbers. Understand exactly what parts you need. The new 5 speed parts are all latest versions. So you must know what is compatible or not with any existing parts that you can reuse. High gear will be late type & must use later bearing in case. You must use later sprocket lock washer. You'll need 2 high gear needle bearings & the seal. You'll want new first gears & the other gears that the service bulletin speak of. Get all this listed by part #. Shipping is not all that costly. About $50. It all worked out for me. I saved well over $300us for the exact same gears & shafts. There is no hidden taxes or tariffs on these dollar amounts. I used paypal to pay for parts. They charge a small fee for exchange rate. Only took about 12 days for parts to arrive to my home in California. Should things go wrong, eBay backs you up. However... you request wrong part or make mistake on part number, that's on you. You must do your homework & triple check your shopping list.

If any US owners are thinking of 5 speed conversion, now is time to do it.
Don


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The article TinkerToo refers to is by Mike James and it can be viewed here:

www.hermit.cc/tmc/technote/mjames/s...ed_Gearbox_Changes_1968_70_MJames_Sm.pdf


Bruce Miller
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Thank you Hermit. On viewing the Gearbox section of the site I overlooked the article. Another very helpful article. The camplate is installed after getting two opinions on the wear, both saying it was fine).
More help was found regarding the gearbox inner and outer covers. The gearbox is ready to install but I'mm too whipped today - I have a cold. Spent 2-1/2 hours repairing the outer cover and it is also sanded to prep for polishing. I'm achy and sore - don't think I'll do anymore today, but who knows, I may feel better later.
Thanks again
Al


Al Eckstadt

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