motor mount or tranny?

i've had this clunking problem for a long time now. it always does it when i take off and i used to have to take off hard for it to do it but now it does it all the time. the other day i noticed that it also clunks as soon as i start the motor. just one clunk. you can feel it in the floor when you do it. it will not do it power brakeing any way but sometimes it will do it shifting into reverse. it also does it when i go over speed bumps. could it be a mount problem? how do i check for it?

check your motor and transmission mounts.

Also check the torsion bar mounts.

how should i check them?

Get under you truck and see if they are bad?