Here's a couple of screenshots showing where the load weight is displayed in the Freight Market and External Contracts screens (click on pics for fullsize).
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Here's a pic of my W900 on the scales with the heaviest load in the base game.
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Here's just the Truck on the scales.
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To get to bottom of your overweight problem you'll have to take a closer look at the mods you are using, unfortunately some mods change aspects of the game completely unrelated to the main purpose of the mod. I also like the game to be as realistic as possible but SCS has to cater for the vast majority of players who just want a truck driving game. Mods can help increase the realism but you have to be careful which ones you use, for every good realistic mod there's at least 10 of the unrealistic/fun type of mod (e.g. 100,000 hp engines). If you upload your game log somewhere (e.g. Dropbox or Pastebin) and post a link I'd be happy to take a look at it for you