I have a 2003 Freightliner Columbia here, ex-Swift, and it has the RTLC-16609E.
It was a direct drive 9, but converted to 13 speed after it left Swift. 0.85 ratio in overdrive.
2.93 axle ratio, just like @WitchingHour mentioned.
That was still a 6-series (old) transmission.
As far as i know, the newer (9-series) convertible transmissions such as RTOC-16909A or RTOC-18909A are 0.73 OD 9 speeds, which can be converted to 13 with 0.86 and 0.73 overdrive (under-drive splitter).