Normally this is caused by a tire out of balance or a bent wheel.
i would really like to know myself
possibilityThe car is out of alignment or you have a wheel out of balance.
It would be highly unlikely.
It would be a transmission issue, not up shifting. If the engine is in "limp mode" it will not accelerate over a set mph.
Tire our of balance or bent wheel. Have your tires rotated and balanced.
Tires may need to be balanced.
problem with your transmission in 5th gear
Check the wheel balance
its not spossed too...you may need to balance your tires
A car traveling over 45 mph can hydroplane with about 1/10th of an inch of water on the road.
Tires need balancing.