When I get on a slope of any kind my coronet with 727 auto just pops out of gear for a second then re-en-gauges. also happens sometimes when i come to a quick stop, then when car re-settles pops back into gear.

 

Low on fluid would be my 1st guess !

 

X2

 

Never heard of fluid popping a trans out of gear sounds to me like a linkage problem, or maybe body flex, or bad trany mount. Is there any rust in the subframe? Starting a hill or sudden stop. Something is moving slightly and then returning quickly.