C series gears - Toyota Yaris Forums

TMX26 · 05-06-2020, 09:31 AM

I’ve looked into this and I can’t seem to find any information about interchangeable gears between C series gearboxes - only interchangeability of the gearboxes themselves.

Specifically for the Yaris 1.5 TS, I find the 4th gear ratio too long compared to the 3rd, and the 5th gear too short compared to fourth. The solution would be a shorter 4th gear.
As far as I know, the 4th gear ratio on the original 1.5 TS gearbox is 1.031. Fitting a shorter OEM 4th gear from another C series gearbox would be an obvious solution.
But for even closer ratios, I was wondering if one could swap the first 5 gears from the C160 gearbox bolted to 20V 4A-GEs into the gearbox of a 1.5 TS (since both are C series gearboxes). The 1st 5 ratios of that gearbox are very close, while still allowing the car to achieve its top speed (loosing only a little in fuel economy). Is this possible ?

Again, I am sorry if this was asked many times before. Thank you for your responses, anything will be appreciated.

CrankyOldMan · 05-06-2020, 08:08 PM

Toyota has done a very good job of spreading their engineering costs for gearboxes by reusing as much as they can from one model to another. The C5X family are not entirely homogeneous though, some have larger axle splines and a different differential housing (e.g. Yaris C50 is physically different than the xD C50). The C15X/C16X family is completely different and incompatible with the C5X/C6X family. There are also differences in the synchro rings and gear hubs but that's mostly improvements over the last 40 years to more reliable components.

I've done a custom C5X gearbox build using parts from a few different models though I've forgotten most of the details. I looked at the taller 4th (0.969) from a early 00's Corolla Hatch/Matrix and I think I put that in mine. ArmstrongRacing did a a lot of research for (and built) a 5-speed and a 6-speed gearbox, one of which had a Kaaz close-ratio gear set for 3-4-5. BlueVitzRS did a C160 swap on his 1st gen Yaris RS but had to swap the bell housing and notch the frame rail to make room. The C60 in Project Vios required the same modifications.

I honestly don't know if the 6-speed gears are compatible with the 5-speed shafts but it's possible that Armstrong documented his findings (somewhere) around here.

CrankyOldMan · 05-06-2020, 08:12 PM

Long winded answer, didn't really answer your question. Yes, the gear sets are generally interchangeable between the same series (C5X with C5X, etc.) but not necessarily between 5- and 6-speed variants, and definitely not between different series (C15X won't fit C5X).

05-06-2020, 09:31 AM	#1
TMX26 Drives: Soon Join Date: May 2020 Location: Switzerland Posts: 2	C series gears I’ve looked into this and I can’t seem to find any information about interchangeable gears between C series gearboxes - only interchangeability of the gearboxes themselves. Specifically for the Yaris 1.5 TS, I find the 4th gear ratio too long compared to the 3rd, and the 5th gear too short compared to fourth. The solution would be a shorter 4th gear. As far as I know, the 4th gear ratio on the original 1.5 TS gearbox is 1.031. Fitting a shorter OEM 4th gear from another C series gearbox would be an obvious solution. But for even closer ratios, I was wondering if one could swap the first 5 gears from the C160 gearbox bolted to 20V 4A-GEs into the gearbox of a 1.5 TS (since both are C series gearboxes). The 1st 5 ratios of that gearbox are very close, while still allowing the car to achieve its top speed (loosing only a little in fuel economy). Is this possible ? Again, I am sorry if this was asked many times before. Thank you for your responses, anything will be appreciated.

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05-06-2020, 08:08 PM	#2
CrankyOldMan 2ZR swap. DO IT! Ask how! View User's Garage Drives: 09 Meteoric Metallic HB Join Date: Feb 2011 Location: West Michigan Posts: 2,333	Toyota has done a very good job of spreading their engineering costs for gearboxes by reusing as much as they can from one model to another. The C5X family are not entirely homogeneous though, some have larger axle splines and a different differential housing (e.g. Yaris C50 is physically different than the xD C50). The C15X/C16X family is completely different and incompatible with the C5X/C6X family. There are also differences in the synchro rings and gear hubs but that's mostly improvements over the last 40 years to more reliable components. I've done a custom C5X gearbox build using parts from a few different models though I've forgotten most of the details. I looked at the taller 4th (0.969) from a early 00's Corolla Hatch/Matrix and I think I put that in mine. ArmstrongRacing did a a lot of research for (and built) a 5-speed and a 6-speed gearbox, one of which had a Kaaz close-ratio gear set for 3-4-5. BlueVitzRS did a C160 swap on his 1st gen Yaris RS but had to swap the bell housing and notch the frame rail to make room. The C60 in Project Vios required the same modifications. I honestly don't know if the 6-speed gears are compatible with the 5-speed shafts but it's possible that Armstrong documented his findings (somewhere) around here.

05-06-2020, 08:12 PM	#3
CrankyOldMan 2ZR swap. DO IT! Ask how! View User's Garage Drives: 09 Meteoric Metallic HB Join Date: Feb 2011 Location: West Michigan Posts: 2,333	Long winded answer, didn't really answer your question. Yes, the gear sets are generally interchangeable between the same series (C5X with C5X, etc.) but not necessarily between 5- and 6-speed variants, and definitely not between different series (C15X won't fit C5X).