Auto Trans help

[griesel72]

I am to the point of finishing up my 72 4X4 project, and i got the motor running, but the trans is another story, i had bought an old parts truck that "supposedly" had a rebuilt 350 trans in it not too much before i bought it, so i figured it would work find, i put a new stall converter in it, and a new filter and fluid, but now when i shift it into drive with the motor running, it will pull the motor down slightly, but won't go forward or backwards. The old fluid i drained out smelled fine, i guess i just don't know what to check first. Is there some easy things to check out first before i give up and take it to the trans shop? (I would hate for it to be something easy and look like an idiot)

thanks
David