We have some Process Gas Compressors here which are Positive Displacement, Lobe Type Compressors from AERZENER. Everything was running smooth for a long time but after Overhauling, the compressors are showing high Axial vibration in the DE side. The Compressors have 2 lobes and 106 gear teeths in the timing gears and are running at 510RPM. Acceleration reading are not so high but the axial velocity reading is too much. Can anybody give some inputs in this problem?