had a problem on a friend of mine jeep a few years back wanted to grind between gears and had vibration problems think his was an 89 or 90 same motor and trans we put a new clutch resurface fly wheel to brg same problem it had a hydrolic clutch sys no adjustment so we replaced the slave and m/c no help so we finaly figured out the clutch pedal has an arm at the pivot point and it was cracked replaced it with new oem part the dealer said they had alot problems with them worked fine for about 6 mo. and did it agean so I took it out bent it back and welded and reinforced it no more problems might want to check this as for the vibration turned out the alternator bracket had broken and the pivot bolt had worn the alt. case hole egg shaped big time funny thing is you could rev the eng and no vib and you could not see the problem but when you drove it felt just like u joints some times these things can fool ya good luck....ted