GHG17 DD Medium Duty Operators Manual Perform a valve lash adjustment as scheduled for the appropriate engine duty cycle. Monitoring the Belt Tensioner DD Platform engines are equipped with an automatic tensioning device. No adjustment or periodic maintenance is required. Poly-V-Belt Inspection Periodically inspect the belts based on the damage guide below. If any damage is noted, replace both belts (Fan and Accessory Belts). A precision wear gauge, available from Gates®, is the preferred method of determining belt wear. All information subject to change without notice. 73 DDC-SVC-MAN-0192 Copyright © 2017 DETROIT DIESEL CORPORATION