Usually seems to be at about 45 mph
Tires need balancing? Bad C/V joint on axle?
replacing mounts on 1994 dodge caravan
Can you elaborate a little? How do you know it's the transmission? Describe the vibration. Is it only at 45 mph? Does it vibrate when you let off the accelerator?
bad u-joints
The first thing I would check is for broken motor mounts. This causes the vibration around 40-45 mph. There is a service / recall bulletin about this at Kia.
Tires
Around 45 mph.
Around 380
bad u-joint on your vehicleor a wheel balancebut i would look at u-joints first
45 mph is equal to approximately 72.42 kph.
The top speed was around 45 mph. Cruising speed was 35 to 40 mph.