STRANGE VIBRATION TRANSMISION?

Ok, this is a little tricky to explain, but I need to figure it out. Whenever I start my truck cold, put it in D or R, then move either direction slowly, it makes this relatively loud intermittent vibration that can be felt through the body. If in the garage, I slowly back out while slightly depressing the brake. When pressing the brake it vibrates and then stops as soon as it rolls then starts again when pushing the brake. It seems there is a correlation between engine run time and trans with the vibration. If I let the truck run for two or three minutes, then it will not do this at all. Even when the truck is warm, it will do this if I don't let it run for a minute or two. The only thing I can think of is maybe the torque converter needs to spin for a bit to get the fluid moving through the trans? I took it in several months ago for a service and asked them to check the Trans fluid. They topped off because it was 3/4 quart low. The vibration exists before and after the level adjustment. Other than the vibration at low speed as described, there is no other indication that the trans is malfunctioning whatsoever. I have often wondered if this is a function of the hill start assist possibly. Does anyone have any feedback on this? Thanks!!

 

Last winter I heard a slight vibration from under the truck while in gear with foot on the brake every now and then, have not heard it for say 6 months. It's more of a buzzing sound and others have complained on this site.

 

Correct, it is more of a buzzing. Sometimes it is there and sometimes not.