I think you mean the friction torque, yes, that should be kept on the high side with a heavy prop. I assume you have a overload clutch installed; so you can check your friction torque to see how much disc spring pressure you have. If you do not have a overload clutch you still need to keep the spring pack pressure high but you need to remove the gearbox and have it checked by a heavy maint iRMT.
The lash is not adjustable, it is the clearance between the gear teeth.
Keith; You should change your gears to 2.43:1 ratio for that long prop. You will be amazed at the thrust increase.
