After going through this entire thread, seeing all the various hypotheses and subsequent findings, I've come up with a few thoughts.
-The gear has been tested to identical harness to previous gears. This indicates to me that the hardness is not the problem.
-OPDA gear wear has been seen on units that show no signs of upper bushing wear or lack of upper bushing lubrication. This indicates to me that the bushing noise is either a secondary affect of OPDA gear wear or possibly even an unrelated issue that may not be resolved by the same fix as the OPDA gear wear.
-The oil pump drive end of the shaft shows increased wear at the corners, indicating less hardness than previous units. Hardness testing of the shaft is needed for confirmation. With as much shaft support is present adjacent to the gear it's hard to see this playing much of a role in the OPDA issue, but would definitely have it's place in the upper bushing lubrication issue.
All these things together leave me with OPDA gear design as the #1 suspect. Not hardness, but the actual shape and profile of the teeth. If they are not angled correctly, or if the tooth profile isn't correct, accurate, precise...excessive and abnormal wear will occur. How else would a gear of identical hardness work just fine? We are also dealing with two meshing gears that don't on the surface appear to even come from the same manufacturer. Where else do you see this? Ring and pinion sets? Transmission gears? All come as matched sets from the manufacturer. If quality control is on the up and up, this can work well but it opens up a door for poor QC to really wreak some havoc.
Side note - I have a transmission output shaft right here with teeth that look better than these OPDA's...and it came from a transmission that failed due to lack of lubrication! Well, except for the gear that failed.
I will be adding some ZDDP additive to my Castrol GTX 10W30 pronto. I will (unlike normal) observe a 3,000 mile oil change cycle for this time around and the next change will get Delo 15W40 diesel oil and an oversized filter.
One more thing...does ANYONE have pictures of a used oil pump drive gear from a model previous to those affected by this issue? I'd REALLY like to see what the wear patterns look like.
I wonder if when the new parts finally show up, whether the priority will go to dealer orders and the folks that order from these sellers will get screwed on the back burner until the dealer network builds a surplus.
I've been through the idea of replacing the gear but I'd like a permanent solution, and I'm hoping the new part from the new supplier will have properly designed and hardened gears, shafts, etc. Unfortunately we won't know until someone gets one and runs it for 10k miles or so. Would be a real shame to see a whole new OPDA designed and sold but use the same gear from some 3rd party vendor and not even fix the problem.
If I was replacing the original part, I would more fully harden the shaft (
) and locate the roll pin hole so the pre-04 gear could be used without drilling. Then I would put an oil passage to the top bushing and put a seal above the upper bushing that could be replaced from the top without removing the OPD assembly.