I just bought a used 2003 Chevy suburban and it was working good, I like to replace certain parts to make sure it lasts a long time and I don't have to worry. I've already planned on replacing the spark plugs, alternator, belts and oil. But before I could get to any of that, today while driving, my husband noticed it was delaying on the gas, than as we turned a corner, there was a clunking noise. Now when we shift gears, its an audibly loud clunk. So in your opinion, should I check the transmission or is it something else? And all the fluids are full, I check those all the time, One of my good habits.