The t-bar can't loosen up and cause vibrations like your describing. If the control arm bushings are really worn out it could cause all sorts of vibrations or knocking noise, but from my experience those bushings usually last a long time. If they are really bad, it should be obvious. When you rotate the tires front to rear, is the vibration still the same? Is the vibration constant or does it only happen when turning? Are you feeling this vibration in the steering wheel?
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*