[V8] checking transmission fluid level

[chris brown]

I was wondering how i can check the level of the transmission fluid on my 1990 v8.. That clunking i get when accelerating from underneath my car only happens when the car is first started and after its warmed up it is barely noticeable.  If it were the drive shaft banging against my exhaust it would do it all the time not just when cold. It literally feels like something is banging on the floor board underneath my drivers seat when i get on it.  Its more like a rattle. Im thinking a pressure plate which is banging around? i really dont know. Remember i had this engine put in about 5 months ago and the sound just recently started. Im stumped.