Chevrolet: automatic transmition w/ no reverse., automatic transmition, tightend

Question
I have a 1985 monte carlo with a 350 and the problem is that I have lost reverse. It will sometimes kick in if the rpm's are high. All the other gears seem to shift fine.  I have already changed filter and fluid but this made no difference. Any insight would be greatly appreciated. Thank you and god bless.

Answer
HI;
you changed the filter did you change all fluid from convertor also . if its not burnt you might need a new tranny . or can you get it adj. see if the bans can be tightend. that might help.If you try to  do it yourself only go a little bit if there is a adj. on it as too much will cause trouble
good luck