Genuine AZ2210040752 synchronizer cone ring for SINOTRUK HOWO 10-speed manual transmissions. OEM replacement for smooth shifting. If your SINOTRUK HOWO truck is grinding gears or refusing to shift into 5th or 6th under load, the problem might not be the clutch — it could be a worn-out synchronizer cone ring, and specifically, the AZ2210040752 unit used in the main shaft cluster of the …