I had the 4l60e in my fiances Gto built at century transmission in Richmond.
Treated us treat great so far.
When we installed it it wouldn't get 3 or 4 but 1-2-r were all working fine. The owner drove up to willowbrook to see what was wrong and it had to come back out. I took it over there a few days later and we pulled it apart, ended up having a hairline crack on the input drum. So part failure not builder issue.
They quickly fixed it (like an hour) and its been in there since. Shifts great, and made that car a ton of fun to drive. I'll take other trans out there to get built when needed. Great customer service.