In the beginning of the film, when the Honda Civic's were hijacking the truck, one of the Honda's drove under the truck. Every truck I have seen doesn't have that much room under it, and usually has a spare tire or other things under them.
This is true, but there are some trucks that are relatively higher so that they can handle a heavier load. Also the cars all had dropped suspension. And i know this does not have much to do with this "slipup" but a standard GT 40 is only 40.5 inches high with a 5 inch ground clearance, imagine what this car would be capable of with onle a 2 inch clearance, it could easily pass under a semi truck.
You are kinda wrong on your slip up. If you ever watched any of the behind the scenes or making of stuff the director tells how htey raised the truck like 4 feet so the car could fit under it without trouble. Thank You