I'm not familiar with the TH180, but I believe I've read somewhere that third is a 1:1 ratio, as is fourth on the five speed manuals. I can confirm that the Tracker four speed is electronically shifted, but it's my understanding that there is a mechanically shifted version of it - Trackers use the 03-72LE, the mechanical version is the 03-72L (the E suffix denotes electronic controls), also known as the A44DL - used By Toyota Volvo & Mitsubishi.