# i-miev motor able to run backwards?



## sholland (Jan 16, 2012)

I am trying to find if anyone has any experience with the i-miev motor in a conversion... I would like to know your opinions if the transaxle can support running this motor backwards, so with the motor on the rear-side of the axle line...


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## brian_ (Feb 7, 2017)

The i-MiEV has a single-speed transmission, with no reverse gear... so it must run backwards for the vehicle to back up. My guess is that the likely issue with turning the unit around would be lubrication of the reduction gears and differential. Sorry, I don't know how the i-MiEV handles lubrication, but if you can get to one or detailed drawings it would help to look for oil flow channels, and for a oil pump.

For comparison, the case of the rear drive unit of a Toyota Highlander hybrid (which is very similar to the i-MiEV unit), appears to be designed so that gear rotation in the forward direction moves gear oil around the housing to where it is needed - it doesn't look like it would lubricate properly if run for an extended period in reverse.


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## major (Apr 4, 2008)

sholland said:


> I am trying to find if anyone has any experience with the i-miev motor in a conversion... I would like to know your opinions if the transaxle can support running this motor backwards, so with the motor on the rear-side of the axle line...


Or run motor same rotation direction having it orientated up-side-down. But there may be problems with lube/coolant if gravity dependent. 

Then again AC motors are generally symetrical with regards to rotation. I think your concerns are in the subsystems like lube and cooling. Anybody have a cutaway diagram of this thing?


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## kennybobby (Aug 10, 2012)

Reverse speed is limited by the controller to about 15 mph, but there doesn't appear to be any limitation in the gearbox why it couldn't run faster. GR is 6.066:1, or 7.065:1 depending upon what you read. That free gear on the input shaft is the parking lock gear.


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## brian_ (Feb 7, 2017)

The drawing is interesting, and there's also a nice cutaway illustration for the first generation of the i-MiEV in an article in _Green Car Congress_: Mitsubishi to begin offering customers test drives of North American spec i-MiEV in November. Unfortunately, neither shows the details of the case which control the oil. While the motor is presumably fine with full speed in the reverse direction, and the gears probably are as well if adequately supplied with oil for lubrication and cooling, it's not at all clear to me that oil flow would be suitable in reverse.


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## electro wrks (Mar 5, 2012)

It looks like the large final gear(with the differential) dips into the lowest part of the gearbox and flings oil onto the other gears in normal forward rotation. In normal reverse, the large gear flings some oil onto the other gears and more away from them. When I've encountered this situation, raising the oil level somewhat has helped. You might try that, keeping an eye on the temp. and watching for seal leakage or blow-out.

Are you going to use the stock single trailing arm, De Dion, Panhard rod, drum brake rear suspension?


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## Duncan (Dec 8, 2008)

As a general rule if there isn't an actual oil pump then gearboxes use splash lubrication and there is normally lots of splashing!

I would be more interested and worried about the helical gear - they are going to end load the shafts that they are on and they may not be designed for that end load to be reversed

The diagram looks as if the end loads are simply taken by the ball races - if they are then you need to check what is holding the bearing into place - normally one is held solidly and the other is allowed to float with the end loads going to the solid one


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## Karter2 (Nov 17, 2011)

If it was designed to run with regen braking, then i would expect it will not be troubled with reverse torque loadings. (Which also reverse the end loading on those shafts)
But reverse rotation of the geartrain may still have implications with splash lube ...though i doubt it.!


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## sholland (Jan 16, 2012)

Thanks for your feedback, that's exactly what I was thinking too... Once I get the unit I will look for external bosses that could possibly be used to run an external pump. I am planning to use this in the rear of a Honda Civic, using JDM 4WD rear trailing arms, so standard rear Honda suspension...


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## brian_ (Feb 7, 2017)

All gearboxes run with loads in either direction - with an engine you have engine braking that loads everything in the reverse direction (while rotating forward), and with any transmission containing a reverse gear some of the gears rotate in reverse with reverse loads. I think there's a big difference between a few seconds of backing up or braking, and running continually under drive load in both the reverse direction of rotation and the reverse loading direction.

The section drawing is in pretty good detail, and shows the bearing races floating away from the housing on the motor side and against the housing on the other side... of all shafts.

I doubt the ball bearings will have a problem with the end loads (as long as they are retained appropriately as Duncan mentioned), but I wouldn't want to count on it with some verification. I hope it works, for sholland and all the other potential applications. At least the motor is water-cooled so it doesn't depend on oil flow.


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