i have a 96 dakota with a 318 and 5 speed. The 5 speed makes aratling noise when u put it in 1,2,3,and when u let offf on the gas

 

are you sure its the transmission itself? it could be a catalytic convertor/or someting else's heat shield rattling, or from my experience, (same symptoms)when you first take off and when you let off the gas the rear end rattles and sounds like its coming from the transmission, RIGHT before it is going to go out on you...

depending on how many miles are on your truck, ide take it to a shop (or do it yourself) and take off the cover and take a look to see if your carrier pin holes arent egg shaped..

im not saying they will be, its just a precaution before it ****s on you.

 

I've a got the same sound but mine is the catalytic converter is going. It makes this terrible rattling sound when you let the engine bog down on mine. It'll do it sometimes while it idles but then stops. Its pretty destinctive, i thought it was my muffler going at first but i had to get underneath of it while it idled and listen.