My 2000 Z28 is an automatic with 160,000 miles on it. Over the past 4 weeks my car, while driving, has started not wanting to accelerate when I get between 50 and 60 mph. Its like it has been put into neutral. Rpms go up but car won't go any faster. It will usually quit if I come to a complete stop or if im on a highway it will stop if i put it into a lower gear manually and then put it back into drive...it then won't do it again the rest of the time I'm driving. It will start back the next time I crank it up to go somewhere. I'm not great with mechanical problems and don't have a clue what the problem could be. This is really the first problem I've really had out of this car.
Any suggestions would be great...
I have heard the word "cylinoids" thrown around several times when I have mentioned something to people who are more mechanical than me but of course I'm not really sure what that is or if it has any relevance to the problem I'm having.

 

Have the PCM scanned for codes. There are transmission codes that don't turn on the SES light, including codes for the shift solenoids.

http://service.gm.com/gmspo/mode6/pd...2000trans9.pdf