My civic jerks/shifts hard when it shifts. What can be the problem? (All mounts seem to be good) thanks in advance

 

Check the fluid. If it has not been changed, drain, refill, drive X3 to get most of the old fluid out.
Verify no codes are stored. Not all codes will set off the CEL or D4 lights.

If the transmission has a throttle valve cable to the throttle body, verify it is properly adjusted. No slack and no preload.

Check the right side cover and look for the shaft speed sensors. Pull them out and verify they are clean and free of junk. If they have ferrous material on them the PCM will not be able to know what the shaft speeds are and shifting can become harsh and/or erratic.

Verify the shift solenoid screens are clean, verify the shift solenoids work by applying battery voltage directly to the solenoids. They should turn on/off with a solid 'click'.

If the transmission checks out, verify the engine is in proper working order. Engine health greatly affects transmission shifting and shift quality. Something as simple as a faulty TPS may not set off the CEL but will cause late shifts that may be considered harsh.