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Hi, does anyone know where I can find information and dimensions for a Tesla Small Drive Unit?
You can find some overall dimension for the small rear drive unit in my build thread (here).

I'm aware of ~10 cars that are currently using the Open Source controller developed by Damien and Johannes (here) and you can expect to see most of the Tesla hardware opened up this year :cool:
 

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Discussion Starter #6
I've made lots of postings about the Tesla Small (rear) drive unit.
www.teslorean.com
TesLorean on DCMTalk.org
TesLorean on DIYElectricCar

If I haven't posted them somewhere else, I can also provide rough (not CAD) dimensions.

Jeff
Thank you. I've taken a look and seem to have come across some dimensions you'd posted a while back. Am I right in thinking there are TWO Tesla SDUs? Front and rear? I thought there was just the SDU and LDU?
 

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Discussion Starter #7
You can find some overall dimension for the small rear drive unit in my build thread (here).

I'm aware of ~10 cars that are currently using the Open Source controller developed by Damien and Johannes (here) and you can expect to see most of the Tesla hardware opened up this year :cool:
Great! Thank you, Kevin. All very useful.
 

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Important consideration from a conversion point of view for the front and rear small drive units, is that for their transmission fluid pumps to work, they must be oriented as they are found in the model S. That is...

front drive unit : motor/inverter leading - differential gear following
rear drive unit : differential gear leading - motor/inverter following
 

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Discussion Starter #11
No problem. If you're in the UK (please add your location to your profile) then Chris Hazell (here) has all Tesla drive unit variants for sale and may provide access to one for measurement if required :cool:
Ha! How weird! I'm also based in Bristol, England! Thank you, Kevin!
 

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Important consideration from a conversion point of view for the front and rear small drive units, is that for their transmission fluid pumps to work, they must be oriented as they are found in the model S. That is...

front drive unit : motor/inverter leading - differential gear following
rear drive unit : differential gear leading - motor/inverter following
It seems reasonable that these drive units must run most of the time in the normal rotational direction, but judging from the drawing and photographs that I have seen, in all cases that means that the motor is behind the axle line. The following image, one a series originally produced by Tesla Motors, shows all of the drive unit variations:

Single motor - RWD with large rear drive unit
Dual motor - AWD with (small) front and small rear drive units
Performance Dual motor - AWD with (small) front and large rear drive units

In this illustration, the small drive motors are in red, and a difference between front and rear small drive units is apparent: the front motor is on the right-hand side, while the rear motor is on the left. That might not matter. (The large rear drive unit has the motor on the left-hand side, but this illustration shows both the motor and the inverter in red.)
 

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Correct, their are two 'small' drive units, front and rear. The front DU stands more upright and has slightly different gearing from the rear.
To explain that further, I think that the front unit places the motor higher to clear the front of the extended case of the 85 and 100 kWh batteries - the overlap of motor and battery case is visible in the illustrations above.

While the HSR catalog says the gearing is the same for both front and (small) rear, I think Kevin is correct, as I have read multiple references to that gearing difference. I believe that the front unit is geared taller (less reduction), so that it is optimized for higher road speed: ~9.73:1 in the rear and ~9.34:1 in the front. Since most discussions of the gearing difference are in Performance models (which have a large rear motor), it is also possible that small rear drive units have the taller (~9.34:1) gearing as HSR says.
 

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To explain that further, I think that the front unit places the motor higher to clear the front of the extended case of the 85 and 100 kWh batteries - the overlap of motor and battery case is visible in the illustrations above.

While the HSR catalog says the gearing is the same for both front and (small) rear, I think Kevin is correct, as I have read multiple references to that gearing difference. I believe that the front unit is geared taller (less reduction), so that it is optimized for higher road speed: ~9.73:1 in the rear and ~9.34:1 in the front. Since most discussions of the gearing difference are in Performance models (which have a large rear motor), it is also possible that small rear drive units have the taller (~9.34:1) gearing as HSR says.


I will find out and post the gearing for the small front and rear drive unit in the next week or so as currently have both opened up to design a limited slip differential


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I will find out and post the gearing for the small front and rear drive unit in the next week or so as currently have both opened up to design a limited slip differential


Sent from my iPhone using Tapatalk

So both front and rear small drive units are geared the same. Info below.

Primary drop = 78/31 = 2.516:1
Final drive = 79/21 = 3.762:1
Overall ratio = 9.465:1



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So both front and rear small drive units are geared the same. Info below.

Primary drop = 78/31 = 2.516:1
Final drive = 79/21 = 3.762:1
Overall ratio = 9.465:1
Thanks Chris! :)

So the HSR catalog is correct.

Fascinating... so the same as one another but different from the 'large' rear iirc :confused:
It makes sense. Both small units were designed for use in the AWD ("Dual Motor") models only. With two motors (even small ones), the gearing could be taller than with a single (albeit larger) rear motor. The resulting mismatch in front to rear gearing when a (small) front motor and large rear motor are combined (a "Performance Dual Motor" variant) appears to be accidental, and it is certainly harmless.

Although some fans make a big deal about Telsa's logic to choose front-to-rear power distribution for best efficiency resulting from that gearing difference, it is just making the best of the accidental situation.
 

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I will find out and post the gearing for the small front and rear drive unit in the next week or so as currently have both opened up to design a limited slip differential


Sent from my iPhone using Tapatalk
Have you confirmed that the differentials in the small drive units are different than those in the large drive units? If not, you can use the Quaife unit from EVTV designed for the large drive unit.
 

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Have you confirmed that the differentials in the small drive units are different than those in the large drive units? If not, you can use the Quaife unit from EVTV designed for the large drive unit.


As Kevin has said they are different. But I have been working with quaife and can now offer a small drive unit abt diff.

I have sole distribution right so if anyone wants one get in contact. Get my first delivery in about 8 weeks.

[email protected]


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