Rep Power: 0

My civic is popping out of 5th gear going up slight hills, and now even on a flat surface. It seems it has gotten worse. I realized it feels like the shift handle isnt going all the way into gear when it is on the ground. However, It goes all the way in gear when I lift the car up with a floor jack and the tire is not on the ground. I am confused. Is it the rear engine mounts fault?

 
Rep Power: 125

If the engine is moving a lot, potentially. Have someone rev the car and see how much it flexes.

Could also be something like a synchro going. 3rd gear is the more common one but I've seen 5th as well.

 
Rep Power: 366

inspect the mounts and see if they are broken. Like said above, check it the assembly is moving too much.

Note: the shifter uses cables, not a hard linkage

 
Rep Power: 0

Its missing the top bolt of the rear t mount and i can't find a replacement. It is longer than the bottom two but every diagram says it is the same size as the bottom one.

 
Rep Power: 222

Go to the dealer, or a junkyard for the bolt

 
Rep Power: 0

got a bolt at a hardware store and changed the oil and it works now. There was very little oil in it.