Hello, over the summer my dad and I fixed up a 1993 Oldsmobile Achieva 3.3 L V6 we had sitting on our driveway for over eight years. Spark plugs, cables, oil and filter, new oil pressure sensor, valve cap seals, front power window motors, a couple heater hoses, recharged the A/C, flushed out the coolant a few times, a new catalytic converter and a tiny vacuum hose. All that was done and it miraculously passed the California smog test. Some would say its money pit! And yes, but it was a fun summer after all and it worked out! It runs pretty good for a 30+ year car with 138 k miles on it. A few months later, now we noticed a tremor when steadily accelerating around the 40-60 mph range. It shakes like its about to fall all apart. I let it get a breath, letting go of the gas pedal and the shaking stops. What could this be? Any suggestions? After a little investigation some YT videos suggest it could be the U joints. Are these difficult to replace? Thanks and have a nice day.