Having transmission problems

[SDELLIOTT1970]

I have a 2005 aveo with about 312000 miles on it, it's a 5 speed. I have been having some issues whenever it's hot outside, 5th gear seems to act up.the warmer the transmission is, the more grind I get trying to put it in reverse. When I drive about 30 miles, 5th gear will go out. It looks like it's going into 5th, but when I release the clutch, the engine races and the RPM 's ramp. Usually the next day it will operate normally. I've been without a usable 5th gear for 24 hours now. The transmission fluid is full. And there may be a bad rear motor mount. Does this sound familiar to anyone? I'd like to know what I am dealing with. Also, changing gears first through 4th are normal. I've become pretty frustrated and just hoping someone can give me some insight.

[Eg.h2o]

I’d drain the transmission oil and check for metallic debris. Clean oil may help…. Even if it looks good, DON’T reuse. Please replace with new fluid. Check for misalignments in the linkage, and also your bad motor-mount may also be contributing to a linkage alignment issue.

[SDELLIOTT1970]

Thank you so much needless to say finding out that it is most likely the shift linkage due to the rear motor mount has been a weight off my mind we first became aware of the motor mount problem when I developed an exhaust leak and turned out it was because all the bolts are coming loose on my catalytic converter plans are in place to replace the motor mount this weekend thanks again