Conserve Mode should only be selected while the vehicle is stopped? (says Rivian Service Center technicians)

[Dark-Fx]

Even this could be governed by software - just wait for the motor torque to ease up before actually disengaging the motors, even after user input.

I don't think there really should be a concern about disengagement. The pawls might stick engaged but once they aren't bound up from torque they should just pop out of the way. I still have no interest in testing it since I like my drivetrain unexplodied.

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[loudog3114]

I have noticed the "clunk" has gone away with one of the recent software updates when switching on the fly. But there was definitely a noticeable clunk when enabling on the fly... if it shouldn't be done on the fly the system shouldn't let you do it.

 

[HaveBlue]

I'm wondering how many of these posters have owned a vehicle with a manual transfer case, a manual transmission or driven an unsynchronized transmission? I can't believe that anything could break under such low engagement forces when it is designed to handle 1000ftlb at full throttle. Just because it is clunking doesn't mean it's broken or will break even if someone convinced the factory to replace parts.

 

[Dark-Fx]

I'm wondering how many of these posters have owned a vehicle with a manual transfer case, a manual transmission or driven an unsynchronized transmission? I can't believe that anything could break under such low engagement forces when it is designed to handle 1000ftlb at full throttle. Just because it is clunking doesn't mean it's broken or will break even if someone convinced the factory to replace parts.

The clutch is just pawls that have square edges. There's nothing that assists alignment/engagement at all as far as I can tell.

 

[Milermore]

I've solved this by taping a big "do not push this button" over the conserve mode. JK.

I have been concerned about kicking the two rear engines in and out at speed and the reported front tire wear with conserve, though, so I just don't use it.
If I have to, I'll add another charge stop to make up for the extra few miles I would have gained with conserve.
I think it's a great idea to be able to switch into 2-engine mode on long flat roads, I guess I just don't quite trust it yet.

 

[HaveBlue]

Yes not unlike most automatic locking differentials like lockrites or Eatons.

 

[TxBeachRivian]

I have an appointment on the 3rd of January, to get the rear half shafts and motors looked at and serviced. While I attempt to recover all wheel drive capabilities. I will let you know what I am told about the ability to switch and how it affects the vehicle.

I can say that I have never had any issue or perceivable problem, until moving into Conserve while coming to a stop, something I rarely do. I actually rarely use conserve, but was trying to get some efficiency estimates in the cold weather and had forgot to switch on my way home, so switched when I remembered.

it was at that point I got the following diagnostic messages.

Got my R1T back today. Turns out my issue was not a mechanical failure or anythIng that requires replacing. Had a loose connector that was not seated well, got it reseated and all is well. Was also told by service that there were no limits on when you could engage.

I will probably limit my engaging of conserve to stopped scenarios just because the warning gave me pause. Until I forget and just engage at anytime again.

 

[DaveA]

For clarification...Per WassymRivian on Reddit....he is the head of UX at Rivian I believe.

 

[R.I.P.]

Got my R1T back today. Turns out my issue was not a mechanical failure or anythIng that requires replacing. Had a loose connector that was not seated well, got it reseated and all is well. Was also told by service that there were no limits on when you could engage.

I will probably limit my engaging of conserve to stopped scenarios just because the warning gave me pause. Until I forget and just engage at anytime again.

Ford trucks have had "automatic hubs" that can be engaged/disengaged on the fly for a long time. Ford will tell you they are designed to work that way, and to use them that way. Techs will tell you to be very careful using these hubs the way the manufacturer advertises them, and will point to a dozen blown hubs in a box under the bench as evidence.

Moral of the story? If you care about your beast, think about what is happening in there and act in a manner that is nice to all those moving parts.

On area of minor confusion, is the fact that when you engage Conserve, you disingage your axles from your motors; opposite of the 4x4 hub example. This means when you engage Conserve at speed, all parts are spinning at the same speed. If you do this under load (accel or decel) the cogs can bind, coming apart with a "pop". This is not the worst thing you can do to the machine, but can cause a lash-response in the drivetrain that will certainly cause premature wear if done often.

When you disengage Conserve at speed, your drive shafts are moving very fast; while your rear motors are not. Connecting these two parts back together at speed would create a rather effective bomb, so one of two things has to happen; either the computer spins the motors up to speed before the cogs are thrown, or a clutch system binds first to sync the speeds of the components (the most common way to do this).

If Rivian is using method #1, that is tricky, and well... wow. I would be surprised. If they are using method #2, then disengaging Conserve at speed is a wear event in the componants, i.e. you are scrubbing material off the clutch plates every time you do it.

Because my brother has his R1T and I am still waiting for my R1S, we took his T out this morning for some testing. He is the type of owner that would rather be nice to his truck, so these are the conclusions we came to:

-Engaging Conserver mode (disengaging the axles) at speed is not an issue, and should not cause any problems long term if done in a power neutral state (throttle between accel & regen).

-Disengaging Conserve mode (engaging the axles) at speed involves putting spinning parts back together, and regardless of method used to sync these, is likely to case wear/damage over time if done improperly.

SO. Want to be as nice as possible to your truck? Engage (which is actually disengaging) at will at speed on the freeway with power neutral. Wait until you are off the freeway and at a stop to disengage (reengaged your axles) Conserve mode.

Whew.

 

[R1Tom]

Just imagine all those posts…”Car pulls to the right when I put it in one wheel drive”

Cool part would be you could switch to one wheel drive, with front right being driven wheel, to counteract the right pull so many experience.

 

[HaveBlue]

Cool part would be you could switch to one wheel drive, with front right being driven wheel, to counteract the right pull so many experience.

Sounds like a cross caster issue. Unless of course all the people complaining are driving crowned roads like in the east. In those cases, alignment shops dial in some left castor. Out west, the roads are flat.

 

[CrazyOne]

The ZF 9 speed used in certain Hondas and FCA vehicles uses a dog clutch. While there were several issues, I believe they are resolved. So engaging a dog clutch at speed is a solved problem, even if it's not trivial.

It is also the biggest reason I did not buy an MDX.

 

[R.I.P.]

The ZF 9 speed used in certain Hondas and FCA vehicles uses a dog clutch. While there were several issues, I believe they are resolved. So engaging a dog clutch at speed is a solved problem, even if it's not trivial.

It is also the biggest reason I did not buy an MDX.

Well, yes. A "Dog Clutch" is method #2. Some variation thereof is how I am sure they are doing this. They should last a good long time, if they are not abused.

 

[AdamUCF]

For clarification...Per WassymRivian on Reddit....he is the head of UX at Rivian I believe.

Don't sell him short... Vice President of Software Development.

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