I have an 08 SEUC3 with 900 miles on it and have heard most of the oil arguments, but has anyone had a trasmission failure from 20-50 synthetic oils?

20-50 is what Harley recommends,and it does the job,so you're not going to have a failure.On the other hand,a good gear oil is better.I am using Amzoil 75-90 synthetic gear lube.To tell you the truth,I think Harley recommends 20-50 in all three hole is to keep it simple,and not having people pouring the wrong oil in the wrong hole.