A4LD Tranny problem
 

I just replaced the tranny in my 86 BroncoII plow truck with a junk yard unit. The tranny seems to shift alright with one exception. When I put the truck into any forward gear from park or neutral It slams into gear hard, doesn't ease in like it should. It shifts into reverse nice and smooth. Any idea what would cause this? one web site I visited mentioned a neutral to drive accumulator, where is this located, and why does it only slam into forward gears? Any info will be appreciated, Thanks