But it simply doesn’t work that way and assuming it does makes the question meaningless. Once on the truck the car is travelling 3 mph relative to the truck and the wheels give a screech and squeal and slow down. Most likely if you didn’t engage the clutch you’d stall the engine.
You were only supposed to blow the bloody doors off!
No it won’t. If the truck’s speed relative to the ground is 60 mph, and the car’s speed relative to the ground is 62 mph, then immediately before the drive wheels hit the ramp, the car is going 2 mph relative to the truck. Immediately after the drive wheels hit the ramp, the car is still going 2 mph relative to the truck, unless you think that the car can instantly accelerate from 62 mph to 122 mph (relative to the ground) at the instant the drive wheels hit the ramp.
It doesn’t matter if you are assuming “theoretical conditions” or not. You can’t change an object’s velocity instantaneously.