Prius V Transaxle surprisingly works fine in a Standard Gen 3B

Hi all. First post here.

TL;DR: You can install a Prius V Transaxle into a Regular Gen 3 and it will work, and will not throw codes.

I wanted to let folks know about a mistake I made, that led to this discovery. My daughter and I did a frame up restoration of a Gen 3B - 2012 Series 2/3. She got the chance to have hands on the engine, and built out the pistons, rings, and bearings herself, and we assembled the engine, Transaxle, as well as essentially everything else on the car. However I digress: The mistake we made with our project, is that I purchased, on eBay, a used Prius V Transmission - wihtout realizing that the Prius V Transmission is actually a bit different from a standard Gen 3 P410. While the casting still says "P410" on the side, the output gear ratio is decidedly different, and therefore power to wheels yields more torque, but with the trade-off of about 13-14% higher overall RPM for the same wheel speed. We assume that this will also mean a drop in MPG.
All of this said, and based on out road tests, we have decided to keep the TransAxle we rebuild installed, as she will be headed to university in a more mountainous region of the USA, and the additional torque may prove to be useful.

Anyways, It was only after we were close to completing the build of the car that I realized this unit was for a "V". So we were concerned that the Gen3B's PMC ECU would throw all sorts of ratio errors, or perhaps the VSC would be angry. However none of this turned out to be the case. The car drives beautifully. The pedal dynamics versus acceleration are definitely different, but it feels like a Prius. So, if you end up needed to do this, I'm letting you know it's possible.

In addition, here are the specifications that I know of about my particular unit that *could* be relevant:

• 2012 Left-Hand-Drive Prius, Series 2/3 [I state it like this as I've never seen a 3B sold up my way without DRL's]
• K Series inverter. My 2013 Prius and this Prius have the identical Inverter. I paid for 3 days of GTS and updated the firmware for both to the latest, with Toyota. If you need i can find the firmware release #
• I don't believe the PMC ECU took any updates, and is the stock unit in the 2012.
• We used a pair of kelvin-rated high-accuracy DVM's an oscillator, a CD supply and an oscilloscope to tune and calibrate the encoders on the TransAxle after rebuild. So nothing special was done to the encoders beside the standard PID flux alignment.
• The Brake Master Cylinder and Pump were replaced with new. The model I purchased was for 2015: Part # 47050-47310. Works beautifully on a 2012 Chassis. This is the only other thing that may have put the car into a place where it could work with the V TransAxle, as this is a *much newer* model than is recommended for the 2012 Vehicle year. The correct model [based on what I can find on GTS] is supposed to be 47050-47180

Anyways, I hope this helps. If you need a little extra torque for some particular application, and you want to stick with a Gen 3 Chassis. It works!
Cheers all...

 

Indeed. Luckily the change is simple. There is one additional hose, and beside that, the hoses, already in the vehicle, will easily accommodate the one additional circuit change. Also you don't have to trim any lines. However if you commit I do recommend trimming off perhaps 4-6 inches of a single hose end.

 

The wheel speed reported for this car is not changed at all, from before, and I can prove this with both onboard GPS's [that we happened to install].
I could, and should, make an entire thread about what I've learned regarding the CAN bus with this car! It's pretty interesting:
Important takeaways, where I've found incorrect assumptions, and I can actually render examples:

• The only place that any portion of a Gen 3 [at least B - so think 2012+] Prius determines wheel speed is both front wheel sensors. But! It must see data from both - regardless of if you are in normal or maintenance mode. If one wheel stops the speed is either halved, or rendered as 0. No data from the back wheels seems to matter for this calculation - although I can try to do this experiment again with another car and could update back.
• The Rotational speed of any portion of MG 1 or MG 2 play no part in the arithmetic used for measured wheel speed.
• The PMC is also apparently not monitoring any expected difference between measured wheel speed and correlation with where it thinks MG2 should be, regarding rotation. In Fact, it appears that, the PMC is not using wheel speed at all and this includes for Cruise Control! It's using a PID of the MG2 rotational speed for Cruise control! This entire time I thought it was [A. using wheel speed, and B. operating KPH in the background - as the "accel/decel" buttons, on my other Prii', all change the speed by 1 KPH at a time - and not by MPH at a time.] Now, I should note!: This is a non-DRCC Prius. So I'll bet that the DRCC Enabled Prii's handle that completely differently. If ever I can afford one, I'll see if I can figure that out.

But there are other oddities that I desperately want to test more, on my next Gen 3B build:

• The Transmission Control Computer [not the PMC] - the unit that controls the operation of the parking pawl motor must be on the CAN bus, and must see a particular set of signals back from the Parking Pawl Motor in before any of the primary safety and motion ECU's - think PMC, and airbag computer, and the main control switch - allow the vehicle, as a whole to determine any status, for power up sequencing or power down sequencing. This is because, from what I can deduce, the Toyota engineers have actually designed the entire vehicle's set of ECUs to trust the location of the Parking Pawl as a final authority of "what the car was doing last". This is genius! as this means that if, through some unusual short, or similar, every computer in the car rebooted at the same time, but the power bus remained online, most of the car will check where the pawl happens to be before it determines even if it should go into Ready Mode. And, from what I can tell, looking at the bus, with a decent Rigol scope, this status is checked before inverter broadcasts any MG rotational speed on the bus. If anyone already knows more about that emergency behavior, I'm all ears! It's pretty cool Until then, I plan to mess about a bit on my next build and learn more.

 

Oh I forgot the other big CAN bus finding! I would be remiss if I didn't mention it:

• The Instrument cluster "owns" the CAN Bus. What I mean by this, is that nothing else, in the car is allowed to send data, in a normal cadence, unless the Combination Meter [as it's called] sends a Start of Frame [SOF]. Or said a different way: Except under dire circumstances, the Combo Meter is the only device that sends an SOF. Now you can get the car to start and sometimes go into ready mode without, as the Tx Control Module can issue SOF's and when it does, the rest of the bus comes alive [for at least that frame]. It's such a "Toyota" thing to do. Have the one device that doesn't effectively own anything about the car own the BUS on which the entire car operates.
• To avoid confusion: consider this separate from proper impedance and resistance on the lines with 120 ohm resistors.

Now this is consistent on both a 2012 and a 2013. If someone has witnessed a normal-cadence without the instrument cluster, let me know - and tell me what was on the bus and what wasn't! I want to test that! Cheers