They have been rebuilding the road from Cody to the East entrance including Sylvan Pass for the last few years. A far as I am aware it has been completed by now. No problem on pulling your 5W as long as you are comfortable driving the typical mountain road. Remember at that altitude (Sylvan Pass 8541 ft) there is only a 3-4 month window to do road work and you guessed it that is when the roads are full of tourists, they only work from about 10PM to 6AM and they CLOSE the road during work hours.