New or Rebuild?
 

So I recently bought a 2006 Cobalt SS as my first manual car. It's the NA LE5 engine and it's been running great (K&N air intake and magnaflow exhaust), even trade for my 2010 LT Sedan. Issue is I noticed a grinding from when I shifted first to second, now second doesn't stay in gear. Since I can put the car in gear when it's off and it'll stay in second it's gotta just be a blown synchro, which from what I've seen will run about $600 for a full tranny rebuild. I could get a transmission with 90K miles for that price and have the shop install it for say about a grand. The current trans has 164K miles on it. Which would be more worthwhile? As far as the car goes it still drives just have to go from first to third which honestly is surprisingly not as bad as I would have expected it to be since third in the car is fine around 20-25 mph hovering around 2k rpm. Just means I have to ride first gear up to about 5500 rpm and go nice and slow off the clutch for a smooth up shift.

Go with the rebuild option. If for nothing else it's peace of mind.

The used transmissions are off a website and come with a one year/3000 mile warranty. I honestly may rebuild then still scoop one to just have a spare in case I find out more synchros are worn or if I ever track it and rip a trans apart. Assumed the grinding into second was because I wasn't used to driving stick when I got it which I'm sure helped to speed up the process of it wearing out but hey. It happens.