Hey all, I haven't snooped on this thread in a while. Sure enough, I find questions when I do! It sounds as if answers were found by some knowledgable folks, thanks for the rescue.
I like to use the flat side of the washers vs the groove side. I tell customers that the thrust bearing will last at least 2yrs using the flat side. Well honestly, I don't know how long they will last. I have several that have racked up multiple birthdays and still perform as new. Occasionally I get a customer that has the thrust cage drop a ball or two. Contact me, I will replace them! Years ago, I used brass cages. Those could have a ball wear enough and could roll up on the cage, locking the system up. No good. I went to stainless retainers and it's been all roses since. The thrust washers are custom ordered with 4.15mm ID on both sides, so no need to go looking for the small or large ID like common thrust bearings have. I do use black Asc grease on the thrust, just a light smear. No need to pack it full. It's just for a little lubrication between the cage and the ball. It really does not serve a purpose to lubricate ball to plate as there is no driving force being applied there (like a spur gear). The thrust bearing does add just a little parasitic drag to the diff action vs a brand new hub bearing, but is far more durable. If you use the groove side, you increase that drag. I have asked my supplier if I could get washers without grooves, the answer was no. So look at it as "options".
The lip on the delrin spacer always goes towards the hub bearing. The delrin spacer is the spring. Some folks like to blend their old aluminum spacer back into the mix. Don't do that! It defeats the purpose of the thrust bearing.
Heads up folks!!!! Some axles are coming with 4mm threaded studs such as Xray and VBC. It's my understanding CRC will soon (if not already) be coming out with 4mm threaded studs. My black anodized nut is 8-32. If you try to use the black nut on your 4mm axle, it could gaul or cross thread, damaging both axle and nut. I will be including 4mm nuts as well as 8-32 in my future thrust kits. So pay attention!
Brian