[VAF84]

Not a youtuber but have 35" and willing to go for that drive!

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It looks really good with those tires!

 

[spiritedEV]

It looks really good with those tires!

Better handling and with a smoother ride.

 

[SilverDan]

on the 3X with 3 Motors it's Virtual locker in the rear and Physical in the front, on the 2X it has 2 Physical lockers one for each of the single front and rear motors.

Checking the web - so the 3X has two motors on the rear which explains the virtual locking/torque vectoring, you're controlling each wheel individually. The front axle, with one motor needs a physical locker. So the SEV's would have one or two physical lockers only (probably two).

Anybody have a schematic of the motor and axle configuration for the SEV? I'm curious how the differential comes into play. Here's the Bolt from Webers vid

Final drive goes through motor center on top, differential at end, the two axles right/left to the front wheels.

In-situ

From the video the second 'idler gear' has a 'counter gear' on it. Not sure what that is there for, maybe some gear-head can explain

So presumably the Hummer has some locker Ultium motor variation - a standard Ultium motor version but with a locking differential. Given GM's new desire to reuse parts, presumably we have two of those in the SEV.

Having worked through this it seems pretty darn likely to me.

 

[nebula1701]

Silverado Rear, Hummer Front/Silverado Front, Hummer Rear

Front Motor teardown:

 

[flyinglow]

There was a patent application a while back for interlocking the diffs on axles with motors on each wheel. For now, you are better off in off-road/limited traction situations having one motor per axle since, in that case, full power can be transferred to the wheel with traction with mechanical lockers. With separate motors for each wheel, e-lockers mean the wheel with traction is limited to the power of that wheel's motor and can even get less as the electronics try to match power to both wheels but are limited by the one with less traction.

 

[SilverDan]

With separate motors for each wheel, e-lockers mean the wheel with traction is limited to the power of that wheel's motor and can even get less as the electronics try to match power to both wheels but are limited by the one with less traction.

Had to think about this for a bit, I think there’s a problem with that logic; it’s actually backwards. With one motor and two wheels on a flat surface, each wheel gets half the total power delivered. With a motor on each wheel, in total there’s twice the power. There’s always more power with more motors.

OK so other extreme is one wheel off the ground. It’s the same for single locked diff or dual motor - there’s only one operational motors with the total power in either case. Either the in air motor is off, or the diff only delivers to the traction wheel.

So you’re talking here about some middle ground where the two motors are trying to match power somehow? Like say there’s a side with slip, so it lowers the power output to that side to keep traction. Here the motors aren’t matched, they’re deliberately using different power levels to maintain traction.

So not seeing what the idea is here …

 

[SilverDan]

Hummer rear dual motor motor, duplicated ports for the two motors

Hummer/Silverado Front, Hummer version has a locking diff. Presumably the diff is built in like the housing? Looks like it would be on the left side output from this picture. If so then a variation.

Silverado back has a diff too, and will probably have a locker if it has any at all.

Now for the interesting question; what if the lockers are already built in but neutered? With low BOM lines like this it’s pretty common to just include dead hardware you neutered out for options, cheaper than having different variations. And would already be the case as the Hummer front uses the locker, with the non TB/AT4 SEV’s having them neutered 👀

 

[flyinglow]

Had to think about this for a bit, I think there’s a problem with that logic; it’s actually backwards. With one motor and two wheels on a flat surface, each wheel gets half the total power delivered. With a motor on each wheel, in total there’s twice the power. There’s always more power with more motors.

OK so other extreme is one wheel off the ground. It’s the same for single locked diff or dual motor - there’s only one operational motors with the total power in either case. Either the in air motor is off, or the diff only delivers to the traction wheel.

So you’re talking here about some middle ground where the two motors are trying to match power somehow? Like say there’s a side with slip, so it lowers the power output to that side to keep traction. Here the motors aren’t matched, they’re deliberately using different power levels to maintain traction.

So not seeing what the idea is here …

Hummer does not have physical connection between the two rear motors in spite of their common housing. From Hummer site: "On some electric vehicles with dual rear motors, such as select GMC HUMMER EV models, a mechanical locker is not required. The vehicle uses software to virtually lock the two motors that power the rear wheels together."

Disagree with your logic based on observations by testers. Mechanically locked single motors perform better than virtually locked dual motors. I realize visualizing it is tricky. I think of it this way. With a single motor, the wheel off the ground isn't providing resistance. It's like it isn't there. All the power is transmitted to the ground regardless of which tire has how much grip so if one wheel is in the air, the other gets all the power. If I come up with a good way of demonstrating it I will post it, but right now I am going on what I have seen in the off-road tests of various vehicles.

With virtual lockers, the traction control computer is trying to equalize both wheels rotation. It has to do that by matching the one without traction to the one with it. What seems to happen is that, if one side has less traction, that motor with traction reduces power in order to allow the side with traction to get traction. In the real world testing, this seems to result in less forward drive. Also, in general, the motors of two motor axles have less power individually than the motor of a single motor axle.

If I find the time, I will try to go back through TFL and Out of Spec off-road tests of Hummers and Cybertrucks with 2 and 3 motors. They both found the results I am referencing.

 

[Rthardison]

Not a youtuber but have 35" and willing to go for that drive!

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Nice. Do they ever rub your fender?

 

[Rthardison]

Hummer rear dual motor motor, duplicated ports for the two motors

View attachment 5508

Hummer/Silverado Front, Hummer version has a locking diff. Presumably the diff is built in like the Bolt? Looks like it woudl be on the left side output from this picture. If so then a variation.

View attachment 5509

Silverado back has a diff too, and will probably have a locker if it has any at all.

Now for the interesting question; what if the lockers are already built in but neutered? With low BOM lines like this it’s pretty common to just include dead hardware you neutered out for options, cheaper than having different variations. And would already be the case as the Hummer front uses the locker, with the non TB/AT4 SEV’s having them neutered 👀

It would be cool to be able to turn on a locker with an aux switch if we could enable on an existing truck!

 

[SilverDan]

Hummer does not have physical connection between the two rear motors in spite of their common housing.

Yah, I wasn't saying so. Actually I was going to write that it looks like the two motors just butt end to end inside the housing along that centerline. Also you can see there's no diff, at least on this side. GM will probably use this motor for other exotica, such as military vehicles.

Disagree with your logic based on observations by testers. Mechanically locked single motors perform better than virtually locked dual motors.

That's a separate question and I'm not disagreeing on performance; which is what it is. What I'm saying is just the physics of it (unless I got something wrong in there), but a force diagram doesn't always translate directly to experience. In this case I think the physical works better because there's no software in-between the driver and the wheels. Virtual lockers are mitigated by a different more complicated control stack which loses that direct feel, plus it's not what people are used to on the road (simpler control stack). But a physical is the same control stack the driver is used to but they have more trail feel because of the physical connection.

Example from a different realm, bicycling. I have two e-Bikes, one is a traditional chain derailleur drive, the other is an (ridiculously expensive German) belt and hub gear. On paper the hub gear is technically better, more gears, equal or better power transmission, and the belt is what is used on performance cars. But the old style chain and derailleur feels better and (feels like it) gives me more control. That's why that's the Mountain Bike (single track), and the hub gear is an all terrain adventure bike (road/fire road). Just like with off roading cars, I depend on the feel of that chain drive (just a single waxed chain/direct gear instead of a belt and complicated gear set) to get me over technical spots and not slip or spill. When rock climbing you need visceral contact and control of that surface.

Anyhow I completely understand what they're saying about the virtual vs physical 'which is better' discussion, but I don't think you're going to explain it using a force diagram; this is in the human realm.

 

[SilverDan]

It would be cool to be able to turn on a locker with an aux switch if we could enable on an existing truck!

In the old days at <some> company (pre fancy encryption software) we would put resistors on the board that would get clipped out to enable the paid for options. Until that is, some canny customers figured this out and clipped them off themselves. 😅 Much cheaper production to produce one widget. Drove people mad but they don't get it, they're not paying so much for a physical thing but the options that mix into the total BOM/margin price.

Now GM's customers take these things apart and are loudmouths, so my guess is they would split off a variant, just to avoid the heartache. If not then in theory you could take the whole motor apart, drill into it, access that control line and hotwire it. A heck of a lot of bother though instead of just buying a Trail Boss. Anyhow watching that Munro disassembly looks like it would be trivial to drop the components in a variant, so the only cost is the inventory (which is more than it would seem). So I think probably not.

I'm pretty confident we'll see dual lockers and I'm hoping there are physical switches on the left hand side for them; I like physical.

 

[SilverDan]

Front Motor teardown:

<Munro boys>

Watching Munro videos always hurts, production wonks criticizing every weld and machining turn makes me want to cry 😅 It's like they think an engineered product is just about the lowest level of production efficiency, when it's much, much much more to consider.

Bean counters basically, it's like the food companies that say "aw damn you know cane sugar is marginally more expensive than high fructose corn, let's use the latter everywhere". Or another one they do "hey you know stopping the production lines for maintenance is costing money, but if we put more oil into the material (e.g. what you eat) then it'll naturally grease the machines and we can keep them running 24/7".

Manufactured food is such garbage in the US because of this this kind of production efficiency thinking; it's a disease and I'm thankful when I see a company like GM not succumb to it. Sure - make production as efficient as you can but don't obsess about it, make your margins other ways. This is why I have a bone to pick with Tesla - sure they produce cars cheap, big deal, but it's the same damn car year after year. Do not ever tell me that's better.

On this one I wish they did the video more like the Weber Auto channel where you can see it semi-assembled. Again a couple of wonks looking with a microscope.

 

[flyinglow]

Hummer rear dual motor motor, duplicated ports for the two motors

View attachment 5508

Hummer/Silverado Front, Hummer version has a locking diff. Presumably the diff is built in like the housing? Looks like it would be on the left side output from this picture. If so then a variation.

View attachment 5509

Silverado back has a diff too, and will probably have a locker if it has any at all.

Now for the interesting question; what if the lockers are already built in but neutered? With low BOM lines like this it’s pretty common to just include dead hardware you neutered out for options, cheaper than having different variations. And would already be the case as the Hummer front uses the locker, with the non TB/AT4 SEV’s having them neutered 👀

I am dubious that the lockers are in the truck and just need to be turned on. That is more of a Tesla strategy. Also, given the total lack of mention of lockers in the articles on the TB/AT4, I do not expect they will have them. GM will likely only offer them with ZR2/AT4X options or trim levels.

 

[spiritedEV]

Nice. Do they ever rub your fender?

I’ve not had issues. It seems to like being on bigger tires. We just returned from a little off-roading, Calypso Trail here in eastern MT.

 

[SilverDan]

Just to drive you guys nuts, here's the locker, two plates with intermeshing ratchets, the actuator is in the lower right corner

Partially assembled, actuator is on the final drive housing, diff with ratchets on the left, you can see how the plastic alignment pins (surely with a metal pin center, the plastic is probably for wiggle) go through the housing on the right under the actuator. It presses on these to push against a spring (probably) and lock against the diff which is in that housing.

The rotational force on that ratchet must be pretty low with the diff gears taking the load, however the statics of it works.

 

[HawaiiEV]

The theory no lockers on Silverado? Maybe on AT4?

 

[flyinglow]

The theory no lockers on Silverado? Maybe on AT4?

The Trail Boss and AT4 will be kissing cousins. If one doesn't have lockers, the other most likely won't. If GM follows ICE truck pattern, lockers and expensive trick shocks will be reserved for ZR2/AT4X options. Those aren't in the most recent order guide so my guess is we have to wait even longer.

 

[HawaiiEV]

I thought the GM rep said the trailboss would have lockers a couple years ago? I think it was a TFL video with the female product manager or something.

 

[SilverDan]

Except for - as I mentioned above - the EV's are more fully optioned with a smaller trim lineup than the ICE's (they already dropped the RST). To get into the TB/AT4 you're spending some serious bucks compared to the ICE versions, a locker costs nothing, dumb move IMO if they leave them off. Plus there's price compression, a ZR2 would have to be back up at $100k for what, some fabric, zippier shocks and lockers? Not even to mention the competition (CT and Rivian) already have them ...

From AI

2025 Chevrolet Silverado 1500 ZR2 starts at $70,995. The price can go up to $79,435 depending on options and trim levels. For example, the 2024 model starts at $71,895 and can go up to $80,335

Lockers, it'll have to have them or be the marketing dumb logic move of the century 😅