Reduction gearbox wear

[Hedobot]

So for the non technical, what exactly is causing the oil to change color ?

For someone brought up on ICE, auto "gearbox" oil was always a nice shade of red and would not be black after a few thousand miles.

[5s Alive]

Hedobot said:

So for the non technical, what exactly is causing the oil to change color ?

For someone brought up on ICE, auto "gearbox" oil was always a nice shade of red and would not be black after a few thousand miles.

Same experience I've had with the prius transaxle. The ATF came out the same transparent red colour it went in.

MTF has a completely different additive package that will permanently coat and adhere to the gear teeth and bearing surfaces. Under pressure and high temperatures these additives turn black and are being continually stripped off and laid down. Theoretically, bare metal surfaces should never be exposed - except perhaps when the gearbox is first manufactured. I would hope that they are pre-lubricated or otherwise protected in some way during assembly.

I'm repeating what I've read on the subject and am fairly clueless about automotive transmissions so don't take the above as gospel. Stripping down engines?, fine, gearboxes?, no thanks.

I think people are concerned that the blackening is suspended metal particles but unless you are seeing a silvery glittering suspension or obvious metal swarf on drain plug magnets or in filters then there's probably nothing to worry about.

[kambites]

If I had to guess, I'd say EVs suffer more from this because with an ICE vehicle, there's sort of natural feedback to stop you from pushing the engine hard when the engine is cold. Even people who know nothing about engines/cars, tend not to push them hard from cold (although obviously there are some oblivious exceptions). EVs have no such feedback loop to cause people to subconsciously treat the drive-train with sympathy until it's at least vaguely warmed up.

Do any EVs limit peak power/torque until the gearbox oil is up to temperature?

[5s Alive]

I've read a few threads where it's been said that not having any requirement to warm up is a plus point for EVs. Perhaps this is not the case after all. The rate that the battery will charge, or indeed discharge (and drive the car) is also quite temperature dependant.

Torque limitation upon start up would be a very simple programming issue. Whether this is implemented or not I have no idea.

I'm discovering more on a daily basis. Especially from this chap - the clearest most easily understood technical descriptions I've ever heard.

[Caddyshack]

5s Alive said:

I've read a few threads where it's been said that not having any requirement to warm up is a plus point for EVs. Perhaps this is not the case after all. The rate that the battery will charge, or indeed discharge (and drive the car) is also quite temperature dependant.

Torque limitation upon start up would be a very simple programming issue. Whether this is implemented or not I have no idea.

I'm discovering more on a daily basis. Especially from this chap - the clearest most easily understood technical descriptions I've ever heard.

I think it would need to be a torque warning more than a limit...imagine pulling out for an overtake and getting much less power than you had the day before when it was warm (I know we shouldn't overtake in that way but people do)

[5s Alive]

Honda CD175, mid overtake on an HGV in the pouring rain, main tank runs dry. Back then there was no warning and you had to physically flip the lever to the reserve tank. Brown trouser moment. It was a particularly daft overtake anyway. I was 17 yrs old.

There was a noticable difference in the Prius between the power available from a flat traction battery vs a fully charged one but not enough to be dangerous.

[Caddyshack]

5s Alive said:

Honda CD175, mid overtake on an HGV in the pouring rain, main tank runs dry. Back then there was no warning and you had to physically flip the lever to the reserve tank. Brown trouser moment. It was a particularly daft overtake anyway. I was 17 yrs old.

There was a noticable difference in the Prius between the power available from a flat traction battery vs a fully charged one but not enough to be dangerous.

I had an E55 AMG (500hp supercharged) it developed a fault on the charge cooler and would massively cut power, caught me out a few times before I realised it was doing it, I think it dropped to about 50% power.

[5s Alive]

Caddyshack said:

I had an E55 AMG (500hp supercharged) it developed a fault on the charge cooler and would massively cut power, caught me out a few times before I realised it was doing it, I think it dropped to about 50% power.

So still twice the 134hp available (most of the time!) from the Prius.

I've only ever driven 500hp cars on a racetrack, slight overkill for Borders A roads but hugely enjoyable when the opportunity presents no doubt.

You can get the occasional unwelcome surprise from the Kona in the wet, when it can scrabble for grip, but that's down to the ultra low rolling resistance tyres. I'm looking forward to binning them but that could be a while as they're barely worn after 13K.

[OutInTheShed]

hidetheelephants said:

It does sound like bearing fit adhesive would be advisable.

It sounds more like a revision of the design would be appropriate.

[hidetheelephants]

Not really an option for owners and independent specialists interested in keeping cars working though.

[5s Alive]

OutInTheShed said:

hidetheelephants said:

It does sound like bearing fit adhesive would be advisable.

It sounds more like a revision of the design would be appropriate.

You may be correct. It appears that Hyundai have given themselves a prickly quality control issue. Their design has 4 main bearings and the motor has two. The slightest assembly misalignment between the motor and the reduction gear input shaft places undue strain on both the motor and reduction gear bearings.

Other designs, as found in ID3/4, have 3 main reduction gear bearings with the motor output shaft sharing the same oversize bearing with the reduction gear input shaft (one sliding splined shaft within another) so manufacturing misalignment is much less likely.

Some appear built to fail but that said there are isolated transmission failures across all manufacturers.

[OutInTheShed]

hidetheelephants said:

Not really an option for owners and independent specialists interested in keeping cars working though.

There's a danger of keeping the box working until the warranty has expired, vs it failing and being replaced by an upgrade.

[kambites]

Caddyshack said:

I think it would need to be a torque warning more than a limit...imagine pulling out for an overtake and getting much less power than you had the day before when it was warm (I know we shouldn't overtake in that way but people do)

I think the suggestion was to limit output until the drive-train has warmed up, not in cold weather. Internal combustion powered cars have done this for years, my car wont let me above about 4000rpm until the coolant is over a certain temperature.