66,000 on my 2017 3500 6.4
Almost all towing my 14k fifth wheel all over California, Utah, Idaho, Arizona, Colorado Texas, New Mexico, Oklahoma, Arkansas, Tennessee etc etc
Seen some very serious grades and heat and freezing cold
changed gears to 456 when it was new
no problems at all
runs very strong
just keep the fluids fresh
hope this helps
had a 2008 1500 crew cab with 5.7 used as a daily driver =no heavy use
put 208,000 on it no issues
sold it to a friend who has put another 35,000 on it with no issues
my current driver is a 2018 5.7 single cab 45,000 on it no issues