Correct sir. Torque AND shock loads bust transmissions.

In a synchro box, when you change gear aggressively to minimise the shift time, first up you rush, with a rapid stick movement, the synchros which have a conical surface that brakes/accelerates the relative speeds of the gears/shaft. That friction needs time (dictates the shift time) for the heat to dissipate - rush it and the synchros burn/wear out.

The other thing that happens is you bring the power back in quickly. The shock load from this is momentarily acting on just one pair of meshing teeth. As you mod and engine and, as a consequence, drive more 'like a thief', the poor old transmission starts to lose teeth - it's a double whammy. The mods load up the box and the individuals who make mods like to use them...

If you have a lot of torque in the above situation, a hell of a lot of heat goes into the synchros and the wallop on the teeth has an inevitable outcome. The shock loads in an aggressively driven synchro box can be pretty evil.

At first read, you might imagine that a zero time shift is even more violent. You'd be correct in realising that there is an instant inertia shock as the engine and input shaft (and the layshaft cluster in many transmissions) have to change speed instantly. ZeroShift (a) reduces the magnitude of the 'shock' with spark cuts or throttle blips and (b) dissipates the residue through the clutch. However, as a precursor to (a) and (b), ZeroShift is dealing with less of speed difference than in a synchro situation.

Also, to answer an earlier post, there is no need (or benefit in so doing) to move the stick quick, or in 0ms! At the end of the stick movement is the ZeroShift mechanism trigger point. While you're moving the stick, you're still in the current gear which means you can, by watching the tacho, anticipate the optimum shift point by moving the stick early and popping it in the hole at the exact correct RPM.

Here are a couple of analogies comparing a synchro shift with a ZeroShift. Imagine two cars driving along the road with a plank of wood across the front.

In a synchro box analogy, both cars are travelling along adjacent to one another, one is driving the plank while the other is idling, 'pulled' by the plank. The effect of pressing the clutch pedal to isolate the engine power from the shift slows both cars. The effect of releasing the clutch (esp. in a hurry) is for the slowed cars to suddenly accelerate up to a faster speed, this time with the cars' push/pull duties reversed. It's a bit like both driving at 60 ... braking to 40 ... then returning to 80mph ... as fast as you can. We have come to accept this is reasonably benign but you can see that, in a hurry, that 40 - 80mph wallop is your 'super quick shift' when racing. All you wanted was 60 - 80 but synchro needs the power removed (consequence: drop to 40) to get you there. A step back to take two steps forward.

In the ZeroShift analogy, the second car is 'passed' the speed difference ONLY. What stops a 'jolt' being felt by the 60mph car when the 80mph car suddenly takes charge of the plank is that the motive power difference is slipped through the clutch (similar to synchro scenario) but it is ONLY the difference in engine speed dictated by the ratio swap. ZeroShift controls ensure the power cut is EXACTLY ONLY that which is required to match the engine to the new gear. Starting from a 60 - 80mph situation (compared with 60 - 40 - 80), 'wallop' is less ... then factor in the clutch/throttle control to get rid of what's left.

Remember, in a constant mesh transmission, all the gears are always in mesh and the output shaft speed (and road wheel speed) is the same immediately either side of the shift event. The clutch isolates the motive power contribution from a jolt from the driveline, aided by a power adjustment to minimise clutch wear. Even without the power cut, clutch wear will be less than a conventional on/off shift. The fact that the power is cut does not reduce acceleration because there is already energy in the driveline driving the car - more energy from the engine isn't needed at this point.

60/40/80 are arbitrary numbers for illustration. The point is that in a synchro box you lose paid-for energy/momentum in a negative acceleration between the two gears - you take a step back to take two steps forward. ZeroShift just takes one step forward.

A last analogy is to imagine turning a nut with a ratchet-handled socket driver. While you tighten the nut at a low speed, a friend with a second ratchet handle comes along and turns his handle faster. Your slower handle now begins to ratchet as it is going backwards relative to your friend.

All the above (I hope!) helps to explain why the shock loads go and why, despite sounding 'violent' at first hearing, a ZeroShift transmission is actually more benign. The relevance to the question is that even just converting a stock synchro box to ZeroShift increases its torque capacity/headroom (a) by being benign and (b) by removing the friction (synchro ring) element from the equation.

Now, if we want to go daft with torque all that's required is finite element analysis on gear/shaft/ZeroShift mechanism dimensions to increase sizes/strengths to meet the new criterion, eg 1000lb/ft, or 2000lb/ft, or...

Final, final answer. It will work a treat in trucks and, more to the point, it will be WORKING a treat in at least one test truck (and a motorcycle!) next year. With trucks, it's not really the '0-60' time that's the driving force, it's the fact that momentum is maintained through the shift. One-step-back-two-steps-forward transmissions are disastrous when you're hauling 25 tonnes up a mountain. Weight/gradient may conspire to make the 'double-step' impossible. Ever seen an artic 'stuck between gears' on the Alps? That's the reason why.