Tech Tip: Triumph T100 Gear Selector Camplates

For today's Tech Tip post we will be covering the two different types of cam plates used (and fitted) to Triumph T100 models from 1959-1974

This also includes the little Triumph 350 twins from 1957-1967..

The camplates (also known as gear selector plates) that we will be covering today come in two variations that happen to be different

Should you be rebuilding a unit 350 or 500 gear box, or perhaps running into "shifting" issues or "popping" out of gear, I recommend that you give this post a thorough read beforing moving forward

Let's dive in 

Triumph Service Bulletin

According to a Triumph parts books and an original Triumph Service Bulletin (dated 1971) there appears to be a total of three (3) variations of cam plates made and fitted to all unit 350 / 500 Triumph models from 1959-1974

Although the Service Bulletin above only describes 2 camplates, there where in fact 3 variations used 

From history and experience, all 3 plates do work and will offer you satisfactory results, however the later plate is "more refined" with a deeper profile and design as described in the bulletin 

Since the later and earlier plates are different, the associated parts that work in conjunction with the plates will be different 

Below we will cover both variations of gearbox camplates and also cover the parts that should be used in conjunction with each plate 

Camplates

Early 57-1768 / T1768 & 57-1458 / T1458 - 1957-1970

Although the Triumph Service Bulletin does not list the true “early” variation, I will showcase it here for the sake of the post 

According to a parts book from 1957-1963, there appears to be a different type of cam plate used and fitted to all 350 and 500 models

Stocked under 57-1458 or T1458

I also noticed that the parts book depicts this particular camplate without a strap but the shift pattern appears to be the same..

In all fairness (and to clear confusion), the 57-1458 plate and the 57-1768 plates are the same, however one has a tie-strap while the other does not

Thickness measures approx .165"

I would suggest using a plate that does have a strap..

When using the came plate 57-1768 or 57-1458 you must use the following parts in conjunction 

The camplate plunger as used on early / mid year plates has a very "shallow" point and must be used with the 57-1458 & 57-1471 plates

Late 57-4218 / T4218

The late style of camplate was used from approx 1971 through the end of production (1974) which can be viewed above 

This particular plate has a thickness of .170"

Notice the strap..

The parts that were used in conjunction with the late style plate are listed below:

The camplate plunger as used on late shift plates has a "sharp" point and must be used with the 57-4218 / T4218 plates only 

Early vs Late

Now that we covered "early and "late" plates above, let's do a side-by-side comparison of both camplates 

If you take a closer look, we have pointed out some of the major differences between the two plates; some visual and some intended by design

Notice that the later plate is slightly longer, has deeper grooves and appears to have a refined shift fork pattern as compared to the early plate that has shallow grooves for gear changing and a more “curvy” design  

Some early and late plates retained the mandatory strap, however, the early type as shown does not..

The strap is designed to keep the plate "rigid" and to prevent flex; similar to early BSA unit twins 

I could only assume Triumph did the "updated" design change to aide with the quality of shiting, gear engagement, and to prevent "popping" out of gear under load..

Installation tips

The Triumph Service Bulletin above states that the later camplate can be used on all models prior, however, when using the later style cam plate (57-4218 / T4218) inside an early motor (pre-1971) you might be forced to remove material around the plunger boss (see photo above) to allow adequate clearance for the later plate 

If you take a closer look at the service bulletin above it appears that you can modify your early camplate to “late” specs which consists of carful grinding, polishing and good judgement  

With parts being easier to obtain now, I would suggest finding a new or good used later plate and retrofitting to your application 

Replacement parts

Should you be working with a worn shifter plate and you happen to be in need of a replacement, finding a “good” used cam plate is going to be tricky 

I have seen many used camplates come up on eBay that happen to be worn in the same places

Luckily we do stock new English made replacements camplates for all unit 350 / 500 unit Twins under the “late” specifications 

See the chart below for all of our current gear box parts and spares that were discussed above for purchase 

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