@hannaz
I'd say that trucks that pull timber are ones that are the most destroyed by its job.
So which can pull more, SLT or that Volvo?
Very true DjordjeC63, these truck shows us that Mercedes are "Truck You Can Trust!"
Regarding Mercedes SLT & Volvo FH750, even I've not came into any conclusion which can pull more. So far there has not been any authorised comparison test of any kind between them, and its even very rare thing to see a proper test review of such heavy haulage trucks in any media. From the specification & facts we can compare Volvo have higher engine output (750hp & 3550Nm) and with crawler gear it claim it can pull 325 tons. Where as SLT may be having relatively lesser engine out put (625hp & 3000Nm) and with Turbo-retarder clutch it has a braking power of 1000hp; the calimed pulling GCW is 250tons. Its noticeable that SLT is more in this business than the Volvo as it has more proven track record in heavy haulage.
Infact the main European competitor in this area for Merc are MAN & with a bigger gap Scania. What an expert quoted me is that, the specialty of SLT is that with lesser engine output & with the use of turbo-retarder clutch it can pull heavy load in lesser fuel which is crucial in such business. Even though the set limit on paper is 250 tons, in most of the condition it is used to pull heavier load. 250 ton capacity is available at 80km/h which means reducing the speed it can pull even heavier objects.
As part of promotional campaign Volvo has done an exercise but pulling 750tons (with lot of effort) as a container road train for a limited distance. I have also read in a forum that Volvo engine is having more power but the mid-range output is less which is again a critical aspect in heavy haulage. In that discussion it was compared to Scania 730hp engine which is said to be a better performer than Volvos 750hp.
So far Mercedes hav not done any such activities, but I have came across few article where SLT was used to pull 550t, 500t, 400tons, etc. in real life condition and 320t & 280tons in off-shore use. But so far the heaviest real life heavy haulage of Volvo I have read was around 220tons. So ideally I think SLT is the real hardcore puller.
PS: for specialised purpose Merc also have Unimogs which is again a proven horse having a capability to pull over 1000 tonnes.