Apologies if this has been discussed before. It seems you can't use these parts together, as there's a slight difference in the diameters of the cylinders in the middle. Incompatibility like this is very annoying. Does anyone know the reason?

Also, is there a table which describes which of the clutching pieces work together?

Thanks :)

The new clutch gears are redesigned to allow pins to catch inside them, which means their axlehole diameter was increased.

It seems like the TLG has been given up the old Driving ring design which has only 2L.
Most of the new clutch-related thing is not compatible with the 2L Driving ring.

Like the yellow extension clutch from 42083 (1x) and the blue and red clutch gear.

The old extension ring is the only old ring that is compatible with the new clutch gears.

Edited December 15, 20195 yr by Didumos69

6 hours ago, Zerobricks said:

The new clutch gears are redesigned to allow pins to catch inside them, which means their axlehole diameter was increased.

This sounds like an interesting explanation for the change, but I'm not sure I fully understand. Can you elaborate?

7 hours ago, Malcohol said:

This sounds like an interesting explanation for the change, but I'm not sure I fully understand. Can you elaborate?

Try inserting a frictionless pin into an older, dark Grey 16 tooth gear and a newer red 16 tooth gear, and you will see. 

11 hours ago, Didumos69 said:

The old extension ring is the only old ring that is compatible with the new clutch gears.

No it isn't quite, its too long to fit inside the new style gears which have clutch holes on both sides. Old extension ring+new style gear=more than 2 studs in length

52 minutes ago, Gray Gear said:

No it isn't quite, its too long to fit inside the new style gears which have clutch holes on both sides. Old extension ring+new style gear=more than 2 studs in length

Well, I'd say the old extension ring is compatible, because it can still serve as a proxy between the old driving ring and the new clutch gears. In fact, when you want to engage the clutch side of a 4L differential with a 20T clutch gear, using a 2L driving ring with an old extension ring is the better option over using the 3L driving ring, because of its extra length. Using the 3L driving ring will give you so much slack that it will slip (image courtesy of @Attika).

I used this myself in a centered heavy-duty manual 4-speed AWD gearbox recently and it works perfectly (Stud.io file here, see the spoiler for the non-AWD version).

Spoiler

Centered heavy-duty manual 4-speed gearbox (Stud.io file here):

 

Edited December 16, 20195 yr by Didumos69

19 hours ago, SamuelYsc said:

It seems like the TLG has been given up the old Driving ring design which has only 2L.
Most of the new clutch-related thing is not compatible with the 2L Driving ring.

Like the yellow extension clutch from 42083 (1x) and the blue and red clutch gear.

16 hours ago, Didumos69 said:

The old extension ring is the only old ring that is compatible with the new clutch gears.

19 hours ago, Zerobricks said:

The new clutch gears are redesigned to allow pins to catch inside them, which means their axlehole diameter was increased.

Exactly! This new 3L driving ring has a bigger "hole" inside that can fit all new and old compatible pars. Informally, all parts could be dived into two groups:

An "Old" V1 group that contains this old 2L driving ring and all parts issued before the new 3L Driving ring:

• 6539 ("red old" Driving Ring 2L)
• 6542/6542b (DBG 16T "single-side clutch" Gear)
• 6573 (Old 4L Diff)
• 32187 (Old Driving Ring Extention)

A "new" V2 group that generally contains all existing parts except the old 2L Driving Ring:

• 18947 ("DBG new" Driving Ring 3L)
• 6542/6542b (DBG 16T "one side clutch" Gear)
• 6573 (Old 4L Diff)
• 32187 (Old Driving Ring Extention)
• 18946 (New Red 16T "double-side clutch" Gear)
• 35185 (New Blue "double-side clutch Gear)
• 35186 (New "yellow" Driving Ring Extention)

Edited December 16, 20195 yr by Void_S
some typos

One reason for the change was it was posssible to put the old grey clutch gears in the wrong way round.
The New Red double face gears overcome that problem.

Edited December 16, 20195 yr by Doug72

2 hours ago, Doug72 said:

One reason for the change was it was posssible to put the old grey clutch gears in the wrong way round.
The New Red double face gears overcome that problem.

Thats not a Problem. Thats people not paying attention 

And the new clutch gears produce more friction too. Old cluth gears ftw

Ok. Great information everyone - that definitively answered my query. I had always assumed that a pin would click into the old 16t clutch gears, but you're right: they don't! I'm reassured that there was a reasonable justification for the change.

Thanks also for the part list! That'll be very useful!

I think there is one other difference between the 2 groups. Because the newer clutch gears are double-sided, there is a small difference in how far the driving ring can insert into the gear. I think a one-sided (old) clutch gear has about 4mm depth for the driving ring and the double-sided (new) has about 3.2mm. those numbers aren't accurate though.

If you removed part of the guiding ribs from the inside of an old 2L driving ring so it would engage with a newer clutch gear, you might be able to use manual selectors, but the driving ring couldn't go deep enough to allow an orange selector gear to rotate smoothly.