Chassis Lubrication

[wesson123970]

I have a 2006 Colorado. I bought it used back in April. I decided I would change the oil in it myself...at least the first few times. I couldn't find ANY grease fittings for the chassis!!I did see several places that looked like they could take grease fittings, but they don't really look like plugs to me...however, they're definitely at the locations that should be lubed. Does anyone know how to change these over to accept grease fittings??...what would be the 'plug' there, actually looks like a long bolt to me, with a 5 or 6mm 'tit' on the end.
do i need to replace that bolt w/ one that will accept a grease fitting?

thanks for the help!

Wes