Why is the trans shifting hard after i changed the plugs

 

Welcome to the forum

I assume an automatic transmission

You may have unplugged a sensor without knowing it

The Computer runs the transmission shifting, when computer thinks there is a problem with the engine, or transmission, it will go into "Safe" mode or "Limp" mode.
This mode will cause direct shifts in transmission, no smooth shifts, that can cause transmission damage if there is a problem.

Are there any other issues after spark plug change?

Also what engine?
and is it 2WD or 4x4?

If possible stop by an auto parts store, they often will Read Codes for free, WRITE DOWN THE CODES!!!!
Don't buy anything and post codes here

 

Randy thank you so much I figured it out already I forgot to plug in the mass airflow sensor and boy let me tell you that **** scared the hell out of me plugged it back in turn the car off turned it back on and that was

 

Good work

Thanks for the update and FIX