i was going to replace the stock speakers in my truck but when i pulled them to check size i found out they were 8ohm. my question is what problems will there be if i put in 4ohm would it damage anything. thank you in advance for your help.
Don't replace 8ohms speaker with 4ohms. Most likely, you own a HU from one of the big 3 car manufacturer. If you must, you can replace it with your home stereo speakers, they are 8ohms standard. By putting in 4ohms, you will overload the stock amp cause it to burn out or go into protection mode. In general, not a good idea.