45 mph is the same as 45 mph. How can one of the two be faster?
I should have said that the car seems to sputter at those speeds rather than shake so I don't think it's a tire problem which most people tend to think of.
It is possible that the shaking in a Pontiac Montana at 45 MPH is the result of failing bearings or tie rod ends.
problem with your transmission in 5th gear
Wheels are probably out of balance or you may have a bad tire.
Tires and/or wheels out of balance?
66 feet per second.
a = (vf - v0)/Δt 10 mph/s = (45 mph - 20 mph)/Δt Δt = 2.5 s