My 2000 s10 LS, 4 banger, 5 speed, two wheel drive, step side has a bad vibration in first and second gear. It's mostly disappears when you shift into 3rd gear. 4th and 5th gears act normally. The clutch and throw out bearing were replaced shortly before I bought and that was about 20k miles ago. It originally started out as a small vibration similar to if you were trying to accelerate in very low rpms. It is my daily driver and got worse over the week so I parked it. Now a few months later I have the money to fix it. Took it for a drive around the block and the vibration is now a shaking. Feels like the whole engine and transmission assembly is shaking. Any ideas?