I have a howl in my rebuild gearbox and would like anyone's insight. I have owned my Dino since 1974. In ’94 the clutch was slipping bad so I pulled off the bell housing to remove the PP/disk/TOB/flywheel to rehab. Since I was there I figured it was time for another valve clearance check and to closely examining the cam lobes. There was at least one low lobe on each cam so I pulled them to send to Megacycle. Short story- I decided to pull the motor and check all specs. While I was pulling the motor apart in my basement I sent the gearbox to a well-respected repair/restoration shop. The head mechanic pulled the gearbox down and said that all the needle bearing were acid etched as well as the Differential Drive Gear and Ring gear. He suggested I replace all and found the “last matched Drive Gear and Ring Gear” in the UK. $4K later I had a rebuilt gearbox- which sat for 10 years (with oil and turned over every few months by hand) before I got it back in my Dino. During my motor rebuild a good friend talked me into restoring my Dino. As those who have done this- it takes longer then you think. It took me 10 years. By the time I had my dino back together the shop had closed and the head mechanic took a job- I do not know where. Soon as I drove my Dino on its first shakedown ride I knew something was wrong. You can barely hear the exhaust note over the howl of the transmission. I have tried different lubes and no joy. The gearbox was always quiet before the rebuild. It is almost painful to drive my Dino. I am thinking that the so-called matched Drive Gear/Ring Gear set is not so well matched- or set up wrong. In a normal differential, you shim based upon blueing pattern on the teeth. I am not sure how the Dino gear set is adjusted- or if it can be adjusted. I do not see any shims in the parts diagrams. Before I break down and pull my motor/gearbox out again- does anyone have any thoughts (or has experienced) on what the cause of the howl/whine could be from. All new bearing as well as DG/RG. Does it mainly under power/load— more so under 3K rpm. Does not howl when on a lift running through the gears. For me, this points to the DG/RG. I still have my old set which does not look bad to me. Open to all theories and plans of action.