My boss has a 98 silverado with a 4L60 that he changed from 3.73's and just put 4.56s in. The truck usually has 35's on it but has 33's on it currently. The truck now that the gears are changed shifts too quickly. It will shift into second before crossing a road and is in over drive by 70km/h. Is there anything he can do that will make it hold gears longer or is it just his tires are to small? He has not had the 35's on it since it got geared.