Torque biasing or limited slip differential for Leaf?

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IssacZachary

Well-known member
Joined
Jan 13, 2017
Messages
881
Location
Gunnison, CO, USA
After getting stuck in the snow with tire chains installed I noticed that the traction control only does so much. One wheel was still completely stuck and wouldn't turn, whereas the other was spinning freely and even dug down to concrete and was chewing away at the concrete. This made it apparent to me that the Leaf would benefit from a torque biasing differential such as a Quaife or a Torsen, or even perhaps a locking or limited slip clutch type differential.

But are any available for the Leaf? Would a differential that fits, let's say, a Nissan Versa fit a Leaf? I would be particularly interested in a torque biasing differential (TBD) vs. a limited slip differential (LSD).

Is there anyone who has done this or felt the need to put a better differential on their Leaf?
 
I wonder how much longer it will be before aftermarket companies start producing parts for the Leaf. It seems to me that there simply isn't anything for Leaf's yet other than rims and spoilers. Everyone has their fingers crossed that Pep Boys will have 40kWh batteries for $1,500 each within a few years. I hope Quaife or someone that make Torsen differentials make some TBD's for the Leaf.

Another option would be to have a differential for another car machined to fit the Leaf. Nice thing about the low gear ratio is that I bet the Ring gear ought to be huge making it easy to fit a fancier diff in there. But I guess a good shovel would be the cheaper option. :)
 
Kristis said:
There are none ;)
Nissan could have emulated an LSD with brakes as with most of the manufacturers, but they didnt...

Interestingly, the service manual says they did exactly this....but if they did it is total rubbish. We hillclimb our leaf, and with hillclimb off it acts exactly like an unlimited open diff out of tight corners

See "Brake Limited Slip Diff" in BRC manual

I'd love to get my hands on a proper LSD, it would really help
 
It does have brake assisted traction control. As far as I understand this system is now mandatory on all new vehicles. But it's not very aggressive in the Leaf. It also limits the torque output of the motor. I'm sure it's better than nothing, but under circumstances like driving through snow drifts with chains on it isn't enough.

The beauty of a TBD and the Leaf's traction control is that a TBD multiplies the torque on the slower wheel. This makes it work great with traction control. If one wheel starts to slip the traction control puts a slight braking force on that wheel. With a normal differential this transmits the same amount of force or torque onto the other wheel, which with the lowered torque coming from the motor might not be enough to get it to go. But with a TBD it would transfer several times (usually about 3 times) the amount of torque onto the other wheel and make it go.

A TBD wouldn't have any friction plates that cause slight energy loses in corners (we need every last drop of energy we can save) and it wouldn't need a special oil either for the same reason.
 
Traction control emulated limited slip on some (all?) vehicles also use a steering angle sensor - if the wheels are not straight it won't emulate an LSD. Have not tested this in the LEAF, but this is how it works on my sisters Challenger R/T (which is an auto with an open diff :roll: )
 
The '11 LEAF at least will easily spin one tire with the wheels pointed straight.

Wouldn't it be nice if Nissan had the traction control smarts that a Tesla has? With many times more power than a LEAF, even in slippery conditions it is able to minimize wheelspin while allowing maximum acceleration, even in conditions that would completely baffle most vehicles.
 
I'd be happy if it didn't cut regen at the slightest bump in the road - particularly going into a corner in B mode with the throttle lifted, can't trust the car in that situation.
 
philip said:
I'd be happy if it didn't cut regen at the slightest bump in the road - particularly going into a corner in B mode with the throttle lifted, can't trust the car in that situation.

Does the Leaf do that? I've been driving around in my Leaf for three months and never noticed it doing that. But then again I don't go faster than 30mph often and usually only have 2 temp bars and one or two regen circles.
 
IssacZachary said:
philip said:
I'd be happy if it didn't cut regen at the slightest bump in the road - particularly going into a corner in B mode with the throttle lifted, can't trust the car in that situation.

Does the Leaf do that? I've been driving around in my Leaf for three months and never noticed it doing that. But then again I don't go faster than 30mph often and usually only have 2 temp bars and one or two regen circles.

The Leaf, like the Prius (Gen III at least) has overly sensitive ABS, and will cut both regen and perceived braking power a lot when a front wheel hits a bump while turning. It can be pretty unnerving, so be forewarned.
 
LeftieBiker said:
The Leaf, like the Prius (Gen III at least) has overly sensitive ABS, and will cut both regen and perceived braking power a lot when a front wheel hits a bump while turning. It can be pretty unnerving, so be forewarned.

I'd argue that cutting regen is actually cutting braking power, rather than perceived braking power. You don't have to be on the brakes at all, just throttle lifted. If you take a corner at speed (near traction limits) and this happens, you will find yourself taking a much wider line than you intended.
 
Yeah the ABS will also cut all braking in a straight line if you brake hard over a bump. Subaru is also known for this and it's common to pull the ABS fuse to just turn off ABS completely. I suspect it's not that easy in the Leaf, but I haven't tried. I use my Subaru when it's really snowy instead.

One thing to point out is that the Leaf at least has equal-length driveshafts which limit torque steer and freewheeling so it could be a lot worse.
 
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