I have a 09 Silverado 3500 with the Allison 1000 6 speed, when you put it in drive and take off, it shudders really bad,after you get above 10 mph it stops vibrating. At highway speed it has no issue, when you come to a stop, it shudders or shakes, really bad. Changed transmission fluid twice and filters , no shavings in the pan or on the magnets, is this the torque converter, is there a solenoid issue? No check engine light or codes. Please advise.