transmission problem

i have an 87 civic hondamatic,every now and then reverse won'twork,but now drive doesn't work at all,1st and 2nd are fine but no drive.
one day when shifting to drive i heard a loud grinding noise and from that day on no drive,but when sitting in my driveway and shifting through the gears sometimes when i shift to drive i get reverse.
i've checked fluid level and it's fine,i'm wondering is it the transmission itself thats gone or could it be something else like filter or something.

It's time for a rebuild.

Usually reverse is part of 1st gear in an automatic transmission. Reverse is actually a band that locks the outer planetary in position causing the inner planetary to reverse it's rotation. If you have a bad bearing, reverse band or clutch pack (yes automatics do have clutches) you could loose a gear.

I blew a sprague bearing on a GM TH350 trans and lost everything but the gear the car was in when it blew. I opened the trans and found that the bearing pieces got caught in other rotating parts and turned the whole thing into shrapnel.