What is involved in replacing a 4L60E with a 4L80E in a half-ton truck?

The transmission bolts to the same LS bellhousing pattern; the work is everything around it:

• A flexplate with the 11.5 in converter pattern (a 4L60E flexplate is 11.062 in).
• A computer that runs it: the factory PCM it came with, or a Holley Terminator X Max (4L60/4L80 control built in).
• A crossmember and driveshaft to suit — the 4L80E is heavier and longer than a 4L60E.

Why people do it: A stock 4L60E is good for about 300–360 lb-ft (≈300–400 hp in a street vehicle); a built street unit about 450–500 hp. The 4L80E is rated 440 lb-ft stock and up to 18,000 lb GVWR. Speedway says heavy vehicles and towing shorten a 4L60's life dramatically.