The reason I changed the radiator is because I have had multiple customers destroy their fresh Good Used Or Rebuilt transmission in less that 30 days because they thought the cooler lines & radiator would be fine with a flush. 1 guy in particular put in 3 used transmissions and they all failed. Then he brought it to me for a rebuild, it had a rear planet set burned up. I recommended he put in a new radiator, but he figured a flush would do it. It lasted 30 days and came back with the same exact rear planet failure. Then he decided to take my advice and put in cooler lines and a radiator. He called 6 months in and thanked me for all the extra work he caused..

The valve-bodies do have their issues. The early 4L60E's used steel valves, the later ones used hardened aluminum valves. Both have caused similar issues in the same wear areas. The valves are both harder than the casting and that causes the wear.

They do need some specialty tools. Most on here have improvised ways to get it done. Me I have been in the trade long enough that I have purchased almost everything that makes my retired life easier... If you read trough some build threads you'll get some idea's for what's needed. "The Transmission Bench series" of video's are good. Just keep in mind that the series is not done by a transmission re-builder but done by a parts guy with a huge shade tree that is selling parts.