# Tesla Small Drive Unit Mounting



## [email protected] (Apr 16, 2020)

Hi,
I am currently working on a build plan to mount a Tesla Small Drive Unit to the rear of a Landrover Freelander 2004 V6. The plan is to have about a possible 200hp from the motor.
Problem is the space at the rear allows me to only mount it back to front meaning since speed in the reverse direction is low(or not a great idea) I am left with the option of mounting it upside down.

Questions: 
1. What is the risk of installing the Tesla SDU upside down apart from oil cooling challenges that might arise? 
2. What other motor options can give the same power/weight/size as the Tesla SDU?


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## brian_ (Feb 7, 2017)

DrJeff said:


> Would you have the option to mount a Front Small Drive Unit rather than a rear Small Drive Unit. That changes the differential from the front to the back.


No, it doesn't. The Model S and X drive units all have the motor behind the axle line... front, rear, small, and large.


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## 4G63T (Jan 9, 2019)

If you need a drive unit so that axle faces toward the rear of the car, I would suggest waiting for the Model 3 drive unit to be available in the near future . 

I am also looking for similar orientation , model 3 drive unit . I emailed EVWest a month ago and they said they are working to have it available in the next couple months or so. I would suggest to wait and do it the way you want or need to . There is also 057 Technology / HSR Motors , I didn’t contact them yet to see if they will have one available soon too. But if you contact them let us know what they say.


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## ViktorT (Jun 26, 2019)

You can mount it backwards so that your reverse becomes forward. You will need to have an external oilpump though as the one in the sdu only works in fwd mode. I think that is easier than mounting it upside down as you would keep the place of the oil level for suction. EV romania has done that in a vw golf


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## Jack-Lee (Mar 29, 2019)

You could switch the tubes in the oilpump! I do this with a small rear drive unit and it works well. So you should switch two of the three motorphases and encoderphases, to turn this Thing in the other direction.


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## ViktorT (Jun 26, 2019)

Jack-Lee said:


> You could switch the tubes in the oilpump! I do this with a small rear drive unit and it works well. So you should switch two of the three motorphases and encoderphases, to turn this Thing in the other direction.


That is very interesting. Do you have any pictures?


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## Jack-Lee (Mar 29, 2019)

The Oilpump is could turn reverse, only the direction of the oilflow change, so you could change the tubes and lets go. But an external electric Oilpump with a filter is better.
The Motorcables could be seen at the picture too.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> View attachment 120021


That image was posted in the DIY Electric Car thread Tesla Small Drive Unit by chrishazell of ZeroEV. Do you have a photo of your own modification?



Jack-Lee said:


> The Oilpump is could turn reverse, only the direction of the oilflow change, so you could change the tubes and lets go.


Can it? Is it a bidirectional gear pump which works just as well in reverse rotation?


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## Jack-Lee (Mar 29, 2019)

@brian_
Sure, somewhere on my phone. Have to search through the thousands of pictures there. The picture here also shows where to start.
Unfortunately I could not open the oil pump without destroying it. However, flow measurements showed the same flow measurement in both directions with the same input power.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> Unfortunately I could not open the oil pump without destroying it. However, flow measurements showed the same flow measurement in both directions with the same input power.


Good to know - thanks.


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## Jack-Lee (Mar 29, 2019)




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## 4G63T (Jan 9, 2019)

^^ If I understand correctly, based on the pics and what your explaining; one would just simply swap the two hoses to run it in reverse ? I assume there is enough clearance for the hoses to cross, clear everything needed etc...


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## Jack-Lee (Mar 29, 2019)

Yes, thats all.


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## tks007 (Feb 16, 2020)

Isaac97 said:


> Any idea how to decode drive unit serial numbers?


Don't know exactly what you mean? I'm able to login into the DU and extract them from a memory location....



Jack-Lee said:


> You could switch the tubes in the oilpump! I do this with a small rear drive unit and it works well. So you should switch two of the three motorphases and encoderphases, to turn this Thing in the other direction.


This is a very nice contribution! Thank u! The phase and encoder are indeed the electrical changes need to 'fool' the design.

Is there a special place where you made this work in the inverter? because there are also current measurements going on?

How do you run the inverter?OpenInverter or Standard tesla? I'm trying to get one going but it looks like the IMMO is in the way...


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## Jack-Lee (Mar 29, 2019)

I use the OpenInverter-Board. Works smooth


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## tks007 (Feb 16, 2020)

My problem is dutch TUV i fear. I need EMC then how do you go along that in germany?
Could we get a TUV documentation for openinverter? then we would be OK too in NL...?


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## remy_martian (Feb 4, 2019)

ViktorT said:


> You can mount it backwards so that your reverse becomes forward. You will need to have an external oilpump though as the one in the sdu only works in fwd mode. I think that is easier than mounting it upside down as you would keep the place of the oil level for suction. EV romania has done that in a vw golf


Cowboy (gypsy?) engineering.

The axial loads on the bearings change direction. 

If you look closely, you'll see roller bearings in that diff. and I wouldn't be surprised to see roller bearings on the other gearbox shafts. 

Those will FAIL because you are using them as thrust bearings by running in reverse constantly and at high torque levels.

To do it right, you need to change the roller bearings out for thrust bearings. You might get lucky to where the bearings can get swapped end for end, but I seriously doubt it.


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## tks007 (Feb 16, 2020)

Basicly what you say is that you need to flip the bearings too?
What you say is that they are xkN in one dir ection and ykN in another?

Flipping should do it then?!?


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## remy_martian (Feb 4, 2019)

Not flipping them around

Exchanging and turning them

Thrust bearing / ball bearing swap with thrust bearing pushing out on the case.

I doubt the case is machined to be able to do that unless there was a really forward thinking design engineer on it.

My open case is on the other side of the continent, so I can't say for sure, but running in reverse makes those helical gears push out on their spindles in the opposite direction.

In reverse, the car is not going fast, loads are usually low, and miles driven is dozens maybe in the life of the car. 

A rule of thumb I'd propose is if the car's gearbox makes a different sound in reverse, under load, the bearings are unsuitable for backwards operation.


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## tks007 (Feb 16, 2020)

I don't know i don't have a open DU to check, but in theory if the load has a direction of rotation then the bearing can be flipped...if you argue that i'm lost...by flipping the direction of rotation of the bearing you basicly undo the direction change. Think about it else there are 2 parts numbers for suchs bearings and there aren't because you can flip them to suit your needs.

The only thing that won't be the same is the play of the bearing. If the play is calculated in the distance between the spurr gears then now the distance will increase or be smaller/tighter but if that happens you will notice on driveing (noise) and its not allot but i must admit that the distance is very crucial for noise..


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## Jack-Lee (Mar 29, 2019)

tks007 said:


> My problem is dutch TUV i fear. I need EMC then how do you go along that in germany?
> Could we get a TUV documentation for openinverter? then we would be OK too in NL...?


You use the "original" Teslamotor.. Nobody looks in this Thing.


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## tks007 (Feb 16, 2020)

Owkey...
Plan C


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## brian_ (Feb 7, 2017)

remy_martian said:


> The axial loads on the bearings change direction.


Yes, this is a potential issue with reversing any gearbox with helical gears. Opposite to normal axial thrust occurs both when driving in reverse and when regeneratively braking in forward motion... both of which are of limited duration and less than maximum torque (and therefore thrust).



remy_martian said:


> If you look closely, you'll see roller bearings in that diff. and I wouldn't be surprised to see roller bearings on the other gearbox shafts.


Yes, in transmissions there are piles of roller (and needle) bearings, and even ball bearings of types unsuitable for high axial loads; the Tesla transaxles certainly have at least those visible roller and ball bearings. On each shaft there only needs to be (and probably should be) only one bearing controlling axial thrust in each direction - that would typically be a tapered roller bearing or an angular contact ball bearing.

Angular contact ball bearings and tapered roller bearings are both typically used in balanced pairs, since a single bearing of these types would be unsuitable even if the axial load on the shaft never changed, so there is unlikely to be problem with anything other than the shaft slopping back and forth with reversals due to free play; that slop would be an issue in normal operation, and not made worse by continual reverse operation. I suppose a potential issue might be a high axial bearing capacity in one direction and a lower (but not zero) axial bearing capacity in the other direction.

Without a complete teardown and examination or an analysis of sufficiently complete documentation, there's no way to know if there is an issue with taking high and continuous axial thrust in the reverse direction. Perhaps someone has done this?


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## Jack-Lee (Mar 29, 2019)

I could send pics from the bearing in a few days.


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## tks007 (Feb 16, 2020)

I would guess they use the same bearings on both sides. Simply because it's easyer with parts stock, and because of regen the load can be quite high anyway on the unit.


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## remy_martian (Feb 4, 2019)

I was talking about the AXIAL loads on the bearing, not radial. If you just turn the thrust bearing around, you're pulling the rollers away from the race vs loading them.


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## remy_martian (Feb 4, 2019)

Roller bearings are cheaper, so they use a roller bearing on one side of the shaft and a thrust (tapered roller) on the other. Let's see what the pics show...


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## tks007 (Feb 16, 2020)

If that would be the case, we need a bit of luck and then you can swap them around, and then you have compensated for the change in direction.

Since the design permits regen, and quite allot and often, I would guess they went for a design in which it can cope in both directions with load.

The forces on overrun (ICE) or Regen (EV) are quite substantial. And imagine a city tour. It's not for nothing that on the picture we see a quite substantial ball bearing


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## remy_martian (Feb 4, 2019)

That would make sense, though regen is still about a quarter to a third of rated power. If there's a tapered roller bearing at each end then no worries.


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## tks007 (Feb 16, 2020)

Yes but the axle diameters are the same so for the sake of parts etc. I would expect it.
Also the design would be ready to be flipped and that would make it also more versatile in the OEM catalogue. For them the direction of the motor is a BIT setting...

I also expect that the angle isn't that big so the forces are not that big. The angle takes away effeciency and improves noise. In the end the biggest amount of force we want is in the forward direction not the side one.

I wonder if they just went with over sized ball bearings since rpm is relatively low, lubrication and cooling is forced. And perhaps the ballbearing is more efficient then the thrust bearing.

Let's wait and see


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## ViktorT (Jun 26, 2019)

Jack, any updates? We are really interested in how it looks


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## coleasterling (Feb 29, 2012)

Bumping this one up. Let's say I'm keeping the rotation stock. Does the angle around the axle matter? I might want to lay it down flat or across the other side of 90 (leaned forward) vs. stock with it leaned back a little. It doesn't seem like it'd be an issue?


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## AusS2000 (Jul 9, 2021)

Any update on this? Is anyone successfully running an SDU in reverse? Or anyone exploded a gearcase?

Noise? Oil pump?


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## John_G (Jun 6, 2020)

remy_martian said:


> If you look closely, you'll see roller bearings in that diff. and I wouldn't be surprised to see roller bearings on the other gearbox shafts.
> 
> Those will FAIL because you are using them as thrust bearings by running in reverse constantly and at high torque levels.
> 
> To do it right, you need to change the roller bearings out for thrust bearings. You might get lucky to where the bearings can get swapped end for end, but I seriously doubt it.


Really now? I suppose you know more about bearings than the TESLA engineers that spec'd them then?

Do explain how these bearings magically change to bearings that are not thrust tolerant, simply by changing their direction of rotation. ROFLMAO....


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## brian_ (Feb 7, 2017)

John_G said:


> Do explain how these bearings magically change to bearings that are not thrust tolerant, simply by changing their direction of rotation. ROFLMAO....


While I'm not saying that I agree with the assessment, I believe that you have misunderstood remy_martian's statement, even though it was clear, and the discussion which followed made it even more clear.

Changing drive direction doesn't change the bearings, but it does change the direction of axial thrust (as remy_martian explicitly stated) due to the helical gears, so the other bearing on the same shaft starts taking the thrust. If the bearings are not the same (not an identical pair mounted in mirror image), there may be an issue continuous thrust in the new direction.


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## John_G (Jun 6, 2020)

brian_ said:


> While I'm not saying that I agree with the assessment, I believe that you have misunderstood remy_martian's statement, even though it was clear, and the discussion which followed made it even more clear.


I respectfully disagree, as he still insists there is something wrong with the roller bearings being used. That is not even wrong it is so far off the mark.



> Changing drive direction doesn't change the bearings, but it does change the direction of axial thrust (as remy_martian explicitly stated) due to the helical gears, so the other bearing on the same shaft starts taking the thrust. If the bearings are not the same (not an identical pair mounted in mirror image), there may be an issue continuous thrust in the new direction.


I agree the direction of focre would change, but clearly he is jumping to unfounded and a speculative conclusion at best. The FACT is TESLA uses roller bearings in all drive units designs and in all positions and they have been modified for reverse rotation (where the issue is lubrication) by many folks without any issues. Which is publically available information.


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## FJ3 (Jun 2, 2020)

I modified my SDU for reversal operation, including the oil pump. It's not just swapping the tubes, you also have to modify the internal pressure regulation valve.
Regarding the bearings; resulting axial forces of the helical gears are taken by symmetrical deep-groove ball bearings which are locked into place in both directions. I don't see any problems.

Have written more info on the OpenInverter forum: Tesla SDU oil pump modification for reverse operation - openinverter forum


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## AusS2000 (Jul 9, 2021)

Cheers. It's good to see someone who has actually done it rather than read the back and forth bickering of armchair mechanics.


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## brian_ (Feb 7, 2017)

John_G said:


> Do explain how these bearings magically change to bearings that are not thrust tolerant, simply by changing their direction of rotation. ROFLMAO....





John_G said:


> I agree the direction of focre would change...


... and with most bearing types that would change which bearing takes the axial reaction thrust, that's all that I was addressing.


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## brian_ (Feb 7, 2017)

AusS2000 said:


> It's good to see someone who has actually done it rather than read the back and forth bickering of armchair mechanics.


Questionable call to attack the members of a forum in your second post. See how that works out when you need assistance or information...


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## AusS2000 (Jul 9, 2021)

brian_ said:


> Questionable call to attack the members of a forum in your second post. See how that works out when you need assistance or information...


If it cuts down responses from bickerers I'll be quite pleased. Alas, I doubt that will happen.


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## ViktorT (Jun 26, 2019)

FJ3 said:


> I modified my SDU for reversal operation, including the oil pump. It's not just swapping the tubes, you also have to modify the internal pressure regulation valve.
> Regarding the bearings; resulting axial forces of the helical gears are taken by symmetrical deep-groove ball bearings which are locked into place in both directions. I don't see any problems.
> 
> Have written more info on the OpenInverter forum: Tesla SDU oil pump modification for reverse operation - openinverter forum


Hi Brian
Im doing the same with an SDU and will change to an external oilpump. Which external pressute regulation valve do you mean in your post?
/V


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## EmmuWisl (Jul 26, 2021)

Giving the amount of time that has passed since the initial post on this thread, I would love to get an update on it. I must admit that I have no idea what is the risk of installing the Tesla SDU upside down, but I do know what will happen if you get into an accident and the car gets upside down. The roof hinge will be blocked, but the door hinge won't be, so the door will just open straight out the side without going up. At https://cararac.com/engine_oil/ you can choose the engine oil you need, according to your car needs, for a decent price.


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## ViktorT (Jun 26, 2019)

EmmuWisl said:


> Giving the amount of time that has passed since the initial post on this thread, I would love to get an update on it.


Im having my project in the workshop mounting the engine. Will post some pics when I have it back. I have checked into the SDU and there are two quite thick bearingrings holding the bearings in place for any axial force in either direction


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## gillisk (Aug 9, 2021)

Has anyone run the SDU upside down? If it was possible to modify the oil feed, then it seems easier than worrying about the bearings and modifying the oil pump pressure regulator. It would be awesome to figure out how to run the SDU this way since they are so much cheaper than the Model 3 rear drive units at the moment (at least in the US).


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## ssiemer (11 mo ago)

Jack-Lee said:


> Yes, thats all.


Thanks for the great post. I am trying to run a small rear S drive in reverse. I split the case and am trying to switch the tubes - but the filler/filter assembly is too tight. How did you get around that? Thanks!!!


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## FJ3 (Jun 2, 2020)

ssiemer said:


> ..am trying to switch the tubes - but the filler/filter assembly is too tight.


It is not just switching the tubes; have a look at this post: Tesla Small Drive Unit Mounting


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## ssiemer (11 mo ago)

FJ3 said:


> It is not just switching the tubes; have a look at this post: Tesla Small Drive Unit Mounting


Excellent information Thanks so much!! I am trying to save 3 dead Zenith vans and hoping I can get this to work....


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