Won't go into gear

So the problem I’m have is it won’t go into gear while the car is running but will when it’s off. What’s the problem

Manual transmission?

Tester

Year? Miles? Engine?

If its a manual transmission its likely something in the clutch system has failed. Does it grind? Or no sound?

Yes manual

04 cavalier 243k no grinding no sound

Look under the vehicle.

And if you don’t see any fluid dripping on the ground, more than likely the problem is with the clutch master cylinder.

If it were the clutch slave cylinder, there would fluid leaking on the ground.

The clutch master cylinder can leak internally where it shows no leaks, but isn’t capable to producing enough hydraulic pressure to operate the slave cylinder to disengage the clutch.

So, this would be like trying to shift without stepping on the clutch pedal while the engine is running. The gears grind.

Replace both the clutch master cylinder and slave cylinder. Because when one fails the other isn’t far behind.

And that should fix your shifting problem.

Tester

No fluid dripping thanks for the input I was about ready to pull the tranny off and replace the whole clutch system