Even the defualt sets of cars in LFS have LSD of some sort, quite a stiff suspension.
You Nissan has an open differntial, comfortable soft suspension, much shorter gear ratios, sure it will spin the front tyre a lot.
XFG with a road going like setup with oped diff spins wheels like mad.
Most of the reasons of your "problems" are your misconfusions of car's differncies so far
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