Trucks struggle going uphill, can barely go over 20km/h at the slightest inclines and a truck will stop completely at the face of a bump / ramp that is over 60 degrees and 1 meter long.
Stopping the truck on hills will make it impossible to continue to drive it forward.
Weirdly, you can reverse a truck uphill faster than you can drive it forward.
Drive over any incline, the trucks speed is extremely low.
Drive the truck up any hill and then stop. The truck won't go forward any more. But it will reverse uphill just fine.
This is a problem with all vehicles but it's mostly noticeable with trucks and armored vehicles and it will be more noticeable once 0.9.6 update goes live and the need for supply trucks climb.