I would be removing a TRTXL to install this T2180. I got 2 quotes; one at $6500 and one "starting" at $5000, to rebuild this one. I haven't called the Mack dealer to see what a reman is usiing this core. I don't put many miles on this truck in a years time. However I would like to pull a pup behind it and adding weight I sure would like the 18 spd. I have and Eaton 13 spd in my road tractor, that has 1.1 mil on it. I bought a RTLO18913 at a salvage yard (as a core) for $2000. It is currently being rebuilt now and I will swap them out sometime in Oct. All total I will have $5500 into it, but will have a spare, working (but worn) 13 spd. If I do the same with the Mack, I will have $6700 into it and a spare, working 12 spd. What is the value of a used TRTXL 1070B 12 spd w/ 240K miles on it???