Transmission oils for EV conversion

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Jan 20, 2014
Brisbane, Australia
Weird question, but I figured this is probably the best place on the internet to ask! I've come into possession of an electric vehicle conversion based upon a recent-model Hyundai Getz which is a front-engine, front-wheel-drive compact car. I'd like to change the fluids since I'm not sure about the quality of the fluids already in there, however I have no idea what would be best to put in it. There's a noticeable performance difference between when the car is cold vs warm, which I attribute to the oils thinning out as they heat up - but without the heat of a petrol engine, that takes a while on this car. Anything I can do to reduce friction is great because it means more range. Keep in mind I'm in Australia for availability, but oil price is almost not a concern since it impacts range & I'll import the good stuff if I have to. I'm not a mechanic but because this is such a unique vehicle I wouldn't expect my local mechanic to know what's best for this car. Can provide photos if it would help. Transmission: this is a manual transmission but not the stock one and I have no idea where it came from. The clutch plate has been removed; the only way to change gears is when the car is stopped (you can take off from 3rd gear without issues so this isn't a problem for normal driving). This also means we spend 99.9% of our time sitting in 2nd gear, and I don't know how this will go over long-term with regards to wear levels. The transmission mates directly to the electric motor & gets a bit of heat from the motor, but constant thickness over a wide temperature range would be great to help those early morning winter starts. I'm honestly not even sure what type, thickness or quantity of oil is currently in there. Should I bother trying to get it tested, and anyone have any leads on suitable testing places within Australia? Given there's no clutch plate would a different type of oil, maybe an ATF, be better? Anyone have any recommendations about what weights I should be looking for, or even a specific brand of oil given I need the most consistent thickness over the widest temperature range that I can get? Diff: This looks stock. Since this gets almost no heat other than what it generates itself through internal friction, I'm pretty sure swapping this with something better will improve my range. What's some options for the best synthetic diff oil that's slick at lower temperatures? And finally - anyone have any idea how frequently I should be changing these oils? Because of the potentially increased wear levels I'm expecting by always staying in the same gear, I'm thinking I might just change the trans oil every 3 years/5000mi. Diff oil is probably fine for the normal schedule.
G'Day... Is this the drivetrain ? Would be hand/fun/good if you can post a pic of the box where the driveshafts come out, as I doubt that they've adapted a new box to the Hyundai diff (you may have 5 gears in reality...maybe). The fact is that you aren't changing gears on the fly, so you don't need to worry about synchro operation, which opens you up to industrial oils if you like...that's only if you like. Given the torque characteristics, I'd like some gear cushioning/load spreading. Given you need economy, you want low viscosity. Maybe something like... Can get it on fleabay. But maybe for a first pass trial synthetic multi vehicle ATF with some
The difference in performance is almost certainly the batteries warming... Guessing the transmission and many other parts aren't going to last very long being used like that.
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Originally Posted By: Shannow
Is this the drivetrain ?
Not that one, but it started out as a different model by that company. Until it broke down & had a major overhaul, replacing a lot of stuff. Now I'm not sure what it is, and communication with that original company isn't an option (I've tried). I'll see about getting some photos underneath the car.
Originally Posted By: horse123
The difference in performance is almost certainly the batteries warming...
100% positive it's not the battery temperature, because the battery temperature doesn't increase that much while driving. Even then, the motor controller limits the peak Amperage well before the battery array gets anywhere close to its rated peak output. I'm making the above assumptions because I'm comparing how many Amps are being used while driving. Maintaining a constant speed down a flat road in your first kilometre in the morning is notably more than maintaining the same constant speed down the exact same road after 20km of errands. The only thing I can think of is that the trans/diff temperatures have increased a little, thinning the oils & lowering their resistance. If nothing else, I'll need to replace the fluids eventually & would like to know now what I should put in there for best performance.
Originally Posted By: horse123
Guessing the transmission and many other parts aren't going to last very long being used like that.
Why do you say it won't last very long, and what many other parts should I be keeping tabs on for future maintenance? Isn't it standard practice to use thinner oils in colder climates? This car is basically a permanent colder climate since it doesn't have an ICE radiating huge amounts of heat under the bonnet. I'm looking for the thinnest oils that will still provide adequate protection, not the thinnest oils I can stick in there without caring about longevity. It's not like there should be a lot of increased wear from the motor swap, either. The new motor is only 37kW/50hp, though it might have a bit more torque than stock but not a whole lot more. And if you honestly think that would be a problem I can just limit its max torque in software.
Honda/Ford/Toyota have a 75w85 GL5 gear oil for the differential. Redline also makes a 75w85 GL5 differential oil. To go any thinner in the diff, need to know the model of differential, vehicle weight, and power of electric motor. Use a full synthetic 75w80 or 70w80 MTF/MTL. If you can find out what trans was used, you might be able to use an ATF. Castrol BOT 303 is very thin and might be available at the GM dealership. Honda/BMW MTF's are another option. Take a sample of your fluids and send it out for analysis, assuming they were filled with the correct fluid to begin with. Nulon, Xado, Pennrite... have the fluids you need if you can correctly identify the diff and manual gearboxes.
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