# Lexus 300h rear drive motor



## brian_ (Feb 7, 2017)

I assume you're talking about the Lexus RX model range. While there was an RX 300 (when the RX had a 3.0 L engine), the hybrid version was the RX 400h or RX 450h (depending on year).

The RX hybrid AWD system is the one from the Toyota Highlander Hybrid; a similar system has since been used in every Toyota/Lexus hybrid model with a transverse engine and AWD.

The rear drive unit is essentially the same as any other drive unit of transversely mounted motor and fixed-ratio transaxle. The motor within it is probably identical to the output-side motor within the hybrid transaxle (MG2), and is sometimes called MGR.

There was extensive discussion of this unit for EV conversion in this forum a couple of years ago. The biggest issue with it might be the lack of cooling: it is only used in the original application for brief periods when extra traction is needed, and will get too hot is used continually at any significant power.

The battery size does not indicate the time for which the rear drive unit can be used, because the hybrid transaxle in the front can supply the required power indefinitely. Electric-only driving (which is very limited in duration and power in any non-plug-in hybrid) would normally be done with the hybrid transaxle at the front rather than the rear drive unit.


----------



## MattsAwesomeStuff (Aug 10, 2017)

This is typically called the "MGR" around here, and there are several people building projects using them.

Yep, they have no cooling lines, so you'd have to plumb your own, a pump, and some kind of small rad. But otherwise they're a great little unit. Compact and super, super light.

The Lexus only ever uses them for very short periods of time IIRC, when power is absolutely demanded. Doesn't mean one way or another that they're not suitable for continuous use, just that they never got it in the Lexus.


----------



## oliverracing (Jan 8, 2021)

Ah, I'd completely missed there was a front motor on the 300h drivetrains too- reading here is sounded like only one motor and I could see rear motors on ebay so assumed that was where it was! (info from here)

If I'm using this as a power boost hybrid then I guess lack of cooling could be ok, but not if it was to be the only motor driving the car all the time. 

I'll add it to the spreadsheet for future research and have a google using MGR


----------



## brian_ (Feb 7, 2017)

MattsAwesomeStuff said:


> Yep, they have no cooling lines, so you'd have to plumb your own, a pump, and some kind of small rad. But otherwise they're a great little unit. Compact and super, super light.


There are no lines because there is no cooling jacket in the unit, right? You can add everything external, but that won't make it a liquid-cooled motor unless you create a cooling jacket. I can't remember offhand what builders ended up doing about this, if anything.



MattsAwesomeStuff said:


> The Lexus only ever uses them for very short periods of time IIRC, when power is absolutely demanded. Doesn't mean one way or another that they're not suitable for continuous use, just that they never got it in the Lexus.


Not just the Lexus - the MGR is not used continuously in any Toyota hybrid. It's used when needed for traction, not overall power. Highlander Hybrids are known to shut down the MGR when trying to get out of an extended muddy area because the MGR has been run too long and gets too hot; it's not fatal (doesn't damage the motor), but it needs to "take a break" and cool down.



oliverracing said:


> Ah, I'd completely missed there was a front motor on the 300h drivetrains too- reading here is sounded like only one motor and I could see rear motors on ebay so assumed that was where it was! (info from here)


There isn't just a motor in front - the front has the engine and power-split transmission that uses two motor-generators to control the engine speed, as well as to regeneratively brake and to boost power using the battery.

Now I see where you're getting the "300h" name. That article is about powertrains - the "300h" part only describes the engine and hybrid system; the model it's in is named by the letters (IS, ES, GS , NX and RC). Most of those models do not use a separate electric-only rear drive unit - they are 2WD. Even with other engines and AWD, the rear motor is not used with the longitudinal version of the system (e.g. LS 600h). The article only mentions a rear motor in the RX, and there has never been a 300h version of the RX model (Lexus equivalent to the Toyota Highlander). The NX (Lexus equivalent to the Toyota RAV4) has a rear motor, and comes as the NX 300h. Other than those rear motors, the motors referred to in the article are in the transmission, not in a drive unit at the rear.



oliverracing said:


> If I'm using this as a power boost hybrid then I guess lack of cooling could be ok, but not if it was to be the only motor driving the car all the time.


I agree, although it could be used as the only motor in a very light vehicle, especially with added cooling.


----------



## MattsAwesomeStuff (Aug 10, 2017)

brian_ said:


> There are no lines because there is no cooling jacket in the unit, right? You can add everything external, but that won't make it a liquid-cooled motor unless you create a cooling jacket. I can't remember offhand what builders ended up doing about this, if anything.


My memory is equally fuzzy.

I think the theory goes, the unit has oil, the oil gets hot. Therefor, drill some holes, add a pump and a rad, circulate the oil so that it cools, now the motor can be run continuously to some degree. And to some degree, sure.

Seems to be a few guys at least making the attempt:



Toyota MGR Rear Traction Transaxle - Page 7 - openinverter forum


----------



## brian_ (Feb 7, 2017)

MattsAwesomeStuff said:


> I think the theory goes, the unit has oil, the oil gets hot. Therefor, drill some holes, add a pump and a rad, circulate the oil so that it cools, now the motor can be run continuously to some degree. And to some degree, sure.
> 
> Seems to be a few guys at least making the attempt:
> 
> ...


It has oil for the gears; that doesn't mean it has an oil-filled cooling jacket around the stator, or any oil flow through the rotor. It might be that it usefully circulates the lubricating oil for a bit of extra cooling through the case, and enhancing that flow and adding a radiator might help.

I only skimmed the last few posts of the OpenInverter thread, not the 150 that preceeded them.


----------



## MattsAwesomeStuff (Aug 10, 2017)

brian_ said:


> It has oil for the gears; that doesn't mean it has an oil-filled cooling jacket around the stator, or any oil flow through the rotor. It might be that it usefully circulates the lubricating oil for a bit of extra cooling through the case, and enhancing that flow and adding a radiator might help.


Indeed.

However, it also doesn't mean that it doesn't. It might have a cooling jacket so that the oil circulates, it just doesn't go anywhere to be cooled. I'm not sure. 



> I only skimmed the last few posts of the OpenInverter thread, not the 150 that preceeded them.


Likewise. I poke my nose in now and then.

I linked that 'cause you're a data junky for torque numbers and one of the guys was just starting to do torque tests on them.


----------



## TT-Man (May 28, 2015)

oliverracing said:


> Looking at the specs the Lexus 300h rear drive motor almost seems too good to be true; 100+kW, supposedly sub 60kg (unconfirmed) and ready to mount to driveshafts as includes the differential so would go in as a straight drop in with some mounts needing to be made.
> 
> Has anyone used one in a conversion? Looking at the battery pack the 300h uses I would imagine the 100kW is peak and not continuous value as its a 1.3kWh pack so would drain pretty quick, but the car can do electric only mode so must be able to be more that just a few seconds.
> 
> For reference, I'm looking at a possiblity of adding a small front drive motor to my RWD kit car and this seems like a good starting point.


Hi All,
I got a rear transaxel from a 350h some 6 or more years ago. The supposed rating was 50kW. We were working on an e- race bike and thought it might be useful. But we never progressed with it. I did some searching and found a US Government site that did a tear-down anaysis of a Toyota hybrid. They tested everything, and one finding was the e-motors were exceptionally short time rated. For example 10 sec. They tested a motor on a test bed and by memory stopped the test at 25kW, half the quoted rating as winding tempetatures were rising beyond the safe values.
Those builders who tried the Toyota rear transaxels, and ..... got them running .... were / seemed disappointed in the performance. A couple of factors, the motor expects up to 650 Vac. So if trying anything less will cut the top speed (back emf and all that).
It is a beautiful little unit, would think less than 60 kg, I can get it off the ground, just, and cannot pick-up an old 112 lb hundred weight!
I thought of having the stator rewound to half the voltage to achieve nearer the motor rating with a say 200 volt battery pack. All now 'pie in the sky'! If anyone would like it .... it is in the Isle of Man. Free, you collect or pay shipping.
Cheers, Joe (TTmann)


----------



## MattsAwesomeStuff (Aug 10, 2017)

TT-Man said:


> If anyone would like it .... it is in the Isle of Man. Free, you collect or pay shipping.


Damien (in Ireland) may want it, and if so, it would likely be used to test, demonstrate, make work, or abandoned, or given away during a workshop. If that sounds like something you'd like to support, consider it, and meanwhile I'll send him a message. It's actively being worked on by several people in the Open Inverter community.


----------



## TT-Man (May 28, 2015)

MattsAwesomeStuff said:


> Damien (in Ireland) may want it, and if so, it would likely be used to test, demonstrate, make work, or abandoned, or given away during a workshop. If that sounds like something you'd like to support, consider it, and meanwhile I'll send him a message. It's actively being worked on by several people in the Open Inverter community.


Hi Matt,
Yes that sounds like a possibility. I will check with my old team on the Island to see if anyone local might be doing an ecar projet. I do not think it likely! Ireland is just 35 miles from our west coast, but a package would probably go around the houses to England, Scotland, into N. Ireland. Unless we find a fishing boat going over, not under CV19 restrictions! And Ah! The new Brexit paperwork. Life gets B' stupid!
Note of interest, what part of Canada? I lived and worked for BC Hydro out of Vancouver some 50 years ago. Cheers, Joe.


----------



## brian_ (Feb 7, 2017)

TT-Man said:


> I got a rear transaxel from a 350h some 6 or more years ago.


Just to be clear, that would have been a rear drive unit (motor and transaxle) from a 2004-2009 RX 400h (there was an RX 350 with a 3.5 L engine, but the hybrid of the era was the RX 400h with a 3.3 L). This would presumably be identical to the 2005-2010 Highlander Hybrid. It could possibly have been from the later RX 450h or Highlander Hybrid.



TT-Man said:


> The supposed rating was 50kW. We were working on an e- race bike and thought it might be useful. But we never progressed with it. I did some searching and found a US Government site that did a tear-down anaysis of a Toyota hybrid. They tested everything, and one finding was the e-motors were exceptionally short time rated. For example 10 sec. They tested a motor on a test bed and by memory stopped the test at 25kW, half the quoted rating as winding tempetatures were rising beyond the safe values.


That makes perfect sense. The RX could accelerate to highway speed in 10 seconds, and once the vehicle is no longer accelerating the rear drive isn't needed. It doesn't have cooling for sustained operation at significant power because it isn't operated for sustained periods at significant power.



TT-Man said:


> Those builders who tried the Toyota rear transaxels, and ..... got them running .... were / seemed disappointed in the performance. A couple of factors, the motor expects up to 650 Vac. So if trying anything less will cut the top speed (back emf and all that).


This would certainly be an issue for anyone using something other than the OEM inverter. Toyota's inverter has a voltage doubler on the front end, to match motor and battery voltages.



TT-Man said:


> I thought of having the stator rewound to half the voltage to achieve nearer the motor rating with a say 200 volt battery pack. All now 'pie in the sky'!


While that could theoretically work, it's hard for me to believe it would be worthwhile, now that there are more suitable drive units from essentially every EV in production.


----------



## DomT177 (Sep 20, 2020)

If its still available, certainly would suit the classic mini I’m converting and would save some costs, (only 17 so cant afford big components atm, saving up for some Tesla batteries)


----------



## TT-Man (May 28, 2015)

brian_ said:


> Just to be clear, that would have been a rear drive unit (motor and transaxle) from a 2004-2009 RX 400h (there was an RX 350 with a 3.5 L engine, but the hybrid of the era was the RX 400h with a 3.3 L). This would presumably be identical to the 2005-2010 Highlander Hybrid. It could possibly have been from the later RX 450h or Highlander Hybrid.
> 
> 
> That makes perfect sense. The RX could accelerate to highway speed in 10 seconds, and once the vehicle is no longer accelerating the rear drive isn't needed. It doesn't have cooling for sustained operation at significant power because it isn't operated for sustained periods at significant power.
> ...


I agree that a rewind would not be an easy option. I knew a local small company who could have done it, but long since out of business. As has been commented, for continuous drive, a cooling system would be desirable. Would not be difficult, by ciculating the lube oil throgh a radiator, but another job! They are a very neet unit. Will put a picture on some time. Cheers Joe


----------



## brian_ (Feb 7, 2017)

TT-Man said:


> As has been commented, for continuous drive, a cooling system would be desirable. Would not be difficult, by ciculating the lube oil throgh a radiator, but another job!


Except that if the oil only goes through the gearbox, it will be nearly useless for cooling the motor.


----------



## TT-Man (May 28, 2015)

brian_ said:


> Except that if the oil only goes through the gearbox, it will be nearly useless for cooling the motor.


Yes, agreed. But the g.b. does have an intimate face with the motor housing, so would help but not optimal. I accept all comments, it is a so near but so far unit. Anybody in the UK, British Isles want to have a go? It is free, except for transport. If it wasn't for the virus I could likely have found someone going over to buy or sell a motorcycle, but Not for a while! Cheers Joe.


----------



## lj516 (Mar 11, 2020)

These are already in full development at openinverter.org and really don't need the full 650V as long as you have field weakening, an MGR paired with a prius gen 3 inverter is a potent pair!


----------



## brian_ (Feb 7, 2017)

lj516 said:


> These are already in full development at openinverter.org and really don't need the full 650V as long as you have field weakening, an MGR paired with a prius gen 3 inverter is a potent pair!


Wouldn't a Prius inverter have a voltage-doubling front end, just like the rear drive unit's stock inverter? The need for high voltage is an issue if using any non-Toyota inverter.

For how many seconds of operation is this "potent", before it overheats?


----------



## remy_martian (Feb 4, 2019)

TT-Man said:


> Yes, agreed. But the g.b. does have an intimate face with the motor housing, so would help but not optimal.


If your goal is to not have the motor face melt, yeah that'll work. 

Otherwise, "nearly useless"


----------



## paaa (Aug 20, 2019)

I would be interested in the motor if still going. Hoping to use on front axle of Subaru legacy conversion to add a bit of power and give me back 4wd (kind of opposite of orinal use case)


----------



## TT-Man (May 28, 2015)

paaa said:


> I would be interested in the motor if still going. Hoping to use on front axle of Subaru legacy conversion to add a bit of power and give me back 4wd (kind of opposite of orinal use case)


Hi, yes it is available and free. But the carriage to Ireland from the Isle of Man could be tricky! Plus covid and all that! What area of the Emeral Isle are you? Someone going over for the road races would be a possible but when will they start up again? Joe


----------



## paaa (Aug 20, 2019)

I will see if I can work out collection from you if that handier for you. Im working in Dublin but based out of Kilkenny.


----------



## TT-Man (May 28, 2015)

Right, I will look it out and check it looks OK. It is in a barn, hidden away.
I'm not in the best of health so give me a couple of days to winkle it out.
Cheers, Joe


----------



## paaa (Aug 20, 2019)

Thanks Joe , No Panic on it just let me know when you have it handy. Also a rough idea of size and weight would be great.


----------



## TT-Man (May 28, 2015)

Hi paaa,
Have located motor differential unit. Guessing the .weight at over 25 kg and less than 50 kg.
Say 40 kgs? Size about 40 x 40 x 30 cms, and 26 cm acros the differential drive flanges.
I feel we need to talk directly. Don't know the etiquette is but my email address is [email protected] and phone no. 07624 330954. You may have a code to add.
Look forward to a contact.
Joe


----------



## paaa (Aug 20, 2019)

I sent an email to you .
Patrick


----------

