I have an ancient Lancruiser from the last generation (1999) that has accumulated over 326,000 miles. We love to drive our cars into the ground, but the “Cruiser” is putting up a good fight. Recently, I noticed (really couldn’t miss it ) that it shakes, rattles and rolls as I drive it and idles louder than usual when stopped and in park. It feels like the doors are going to fly off when I am going between 40-50, but is less noticable at higher speeds. It is detecable at slower speeds, but not as extreme as it is at mid-speeds. I am thinking it may be the muffler because of the louder exhaust sound when idling. However, I’m not sure how/why the muffler would make the car shake when driving. Otherwise, it works well (if you discount the sporadic functioning of the windows - usually at a drive through restaurant or drive-in bank teller. Thoughts?
A bad muffler could change the back pressure of the exhaust system and impact on how the motor runs. Good idea to get it fixed, safer for you too since exhaust fumes and CO2 are bad for people and pets.
The shake could be something unrelated. If you got a bunch of mud in your wheels and tires that could unbalance the tires. Check the wheels for caked on mud. You could have an old tire or two going bad on you. Belt separation will unbalance a tire and put it out of round causing a shake. Since the truck is so old there are CV joints and U-joints in the drive train that do go bad and with those kinds of miles a bad joint in the drive train is very possible.