On the contrary, Syncro, due to the "hump phenomenon", (about which you can find here and here), transfers the total, 100% of the torque, to the secondary axle.
In the above video, the owner of the Audi Quattro TT, (but Audi Haldex in reality, since Audi uses the term "Quattro" to name and the Haldex cars, which are these with transversely installed engines), engaging the handbrake, discovers, (with desperation I suppose), that the rear axle is neutralized, due to the inefficiency of the system to overcome the friction of the rear brakes.
But, in the real life use does this, really, matter?
(Especially if you know what the Syncro can do...)
I 'll let you decide:
22/May/2018
This never happens to a Syncro:
26 March 2023
The inner vw 4x4 comparison systems, t3 Syncro, t4 Syncro & passenger Syncros, t5 Haldex, t6 Haldex.
Digging deeper…
The t3 has a “gelande”, (extremely short), gear for rock crawling and vertical walls overcoming. A tremendously important tool, because multiplies the engine torque as it is distributed through the kinematic chain.
Another aspect, unique for the t3, is the front, (optional), locker which, cannot be compared to the EDL, for the off road, the other 4x4 vw buses have, since it can feed, if it is needed, just the one front wheel, with 100% power, smoothly and without the clicking effect of the EDL, which EDL, transfers torque in a very limited portion using the brakes.
The VCT of the t3 is unique, also, since is protected into a cell and it is liquid cooled, a really heavy duty VCT, BUT just for the front wheels.
And here is another superiority of the t3, since, when loaded, the power is needed to the rear axle mainly, where the load is, especially when there is an obstacle. The t3, and only the t3, has gears to drive the rear axle where the others have “soft” solutions, VCT, (t4), or, especially, HALDEX, (t5, t6). For the t3, the rear axle is the primary, and one more heavy duty structure, and the front axle is the secondary, best architecture for a, heavy duty, military tool, 4x4 car.
Here is a comparison between the t3 SYNCRO VCT and HALDEX:
http://www.vwsyncro.eu/p/vs-t5-4motion-haldex.html
Syncro HUMP phenomenon, and why the Syncro VCT is capable to transfer from 5% up to 100% of power, at demand, smoothly, without vibrations, at any speed, without limits, without service, (or with very limited, in the worst case scenario), (no, HALDEX cannot):
http://www.vwsyncro.eu/p/blog-page_5.html
Now, both bus/van Syncros, the t3 and the t4, and the passenger Syncros, the year 1988 and after, may use their handbrake to lock the rear differential in the case the rear locker is not available. And you now something? When you engage the handbrake you brake the 4 wheels simultaneously! Very useful as a hill descent control for the t3, the t4 and the passenger Syncro model range.
The t4, with the exception of the, optional, rear locker, has the same Syncro system as the passenger Syncros have, the year 1988 after, (b2, b5 Syncro excluded, they are Quattros). And it has an extra free wheel structure, which stabilizes the car under heavy braking. Both, t3 and t4, may lock the rear and the front differentials, just by applying their brakes.
