This weekend I installed a PI torque converter in my 95 Aod-E. When I am backing up or going forward slowly.....it feels small vibration or a chattering is happening. I went with the 2800 stall. When I drive it, the vibration goes away but when you back up or drive forward on low RPM's you can feel it. What could be causing this to happen? the torque converter was put into the trans right and was torqued to the flywheel by specs. Thanks