i recently installed a front 3in lift block on the front and 1.5 add a leaf on the rear. ever since i put the lift on i would get a slow vibration/hum around 10mph-45mph, it will get faster as i go but when i hit highway speeds its not noticeable. its not a constant hum or vibration it'll be like humm----humm----humm with about 2-4second interval. i tried dropping the front diff with spacers i fabercated (did this with my 08 tacoma with no problem) and the carrier bearing but still didn't make a difference. BUT i did notice it stops humming when i switch it 4wd.... im lost and never had this issue!! HELP