In Part 3 we are going to test fit the C60 internals into the C50 case and shoot for a final assembly. First we need to take some measurements to verify the C50 bell housing bearings are compatible with the C60 shafts and differential. Lets get started:

When you have been repairing transmissions for several years, you can tell by looking at a gear set wether or not it has been abused. This junk yard C60 is one of those transmissions that likely saw many drag races and probably some street racing as well. The main giveaway is usually damaged synchro teeth, but thats never the full extent of the problem. This visual cue is what prompted me to contact my teammate John on what direction to go, so here is where Part 2 begins. A full teardown,  close inspection, and repair. 

Here in Part 1 we will be disassembling the 2003 Toyota Celica GTS C60 transmission and comparing parts to the common C50 5 speed. The bell housing on the C60 has a different starter orientation and the rear mount attachment is different. We are hoping the 6 speed parts can be installed in the 5 speed case, making it a direct fit. The tools required to disassemble and service these transmissions varies, and gears can break when stressed in the wrong areas. Armed with that information, please proceed with this project at your own risk and consult a transmission specialist if you are not comfortable. Now, Lets get started:

I'm aware this may be an ancient discussion, but since Im just now entertaining the idea of a 6 speed swap (I'm going to assume you've seen the Teaser Video) ...lets take a look at the numbers for a minute. A lot of modern sports cars have 6 speeds, so they must be better right? Maybe....or maybe not.

To learn the technical answer we need to first consider our engine, and additionally each of us may have a different idea of what's "best". So lets look at our 2ZRVIOS. We have a Toyota 2ZR-FE Dual VVTi engine making 139HP @ 6000rpm/131FTLBS @4100rpm. You can see here that our power band is from 4100rpm to 6000rpm, so we need our gearing to keep the engine speed in that range. Now if you can remember our ARtrackbox build, a Yaris C50 transaxle with the Cusco  Type-RS LSD and a Scion 4.3 final drive. This transmission has awesome acceleration and provides flawless grip under all racing conditions.  Aside from its limited 5th gear, the C50 ratios are a perfect match for the 2ZR-FE.