I have a 2005 Neon SXT, it has about 140,000 mi. on it, and a 5-speed manual T350 transmission. It recently began slipping out of gear when it gets to about 2300 rpms. This happens in all gears. This occurred intermittently at first , but seems to be doing it everyday now. Sometimes turning the engine off for a few seconds will keep it from doing that for awhile, until maybe a day or two later.
I assume that my clutch is failing? Could it be anything else?

Also, CEL has been lit for awhile. I cycled the key and got the following codes:
P0129, P0325, P0456, and P0340. Where can I find a list of code definitions? Thank you for any help!

 

Don't know about the codes but check the rubber bushings under the gear shift lever that connect the shift rods to the gear shift lever. When these wear out or crack and break, the shift levers do not let the transmission gears fully engage. We found that on one of ours.

 

Thank you beanspotjr. I googled and found a "How-To" on changing the bushings, and it appears to be fairly simple. I will see if mine are worn out. The how-to I found recommends replacing them with Booger bushings; any thoughts on replacements?

 

I checked the bushings that connect the shifter to the shifter rods, and they look just fine. There is no slack in the shifter either, so I don't think the problem would be these bushings.

Any idea as to what else it could be? Thank you for any help!

 

I still think you may have a problem with each shift position engaging completely. Thus, check the bushings where the shift rods connect to the transmission and check the amount of travel the rods have at the transmission. If there isn't full engagement for each shift position, it will pop out of gear. I don't think the clutch would cause this problem.