[R.I.P.]

I started out on the "other" side of this argument, but got schooled by the real world. For the purposes of this discussion, I will be just talking about the quad-motor design, but the Tri-motor (Hummer, Tesla) will have the same limitations on any axle with two motors.

Let's start with with my new position on the matter; The quad motor design is at a significant disadvantage when compared to a vehicle with differentials on certain low traction surfaces.

I got a lot of blow-back on this topic on other forums, mostly from people who were not even driving the truck. Weird. I am certainly open to discussion on the topic, that is what these forums are for, but please... please have a very good operational knowledge of "rolling friction" and the torque vectoring characteristics of the differential when joining the conversation. "No, you are wrong" is not an informed position.

Let's start by establishing the three modes a differential can be used in:

1. Open
2. Limited Slip
3. Locked

Next let's establish that a quad has no differential, so it must emulate these modes to address different traction needs.

1. A quad has no way to effectively emulate an open differential. It always tries to apply torque to both sides.
2. A quad is relatively good at emulating the Limited Slip mode. In fact, it is what it is best at.
3. A quad has no way of fully umulating fully locked mode

Now to explain those three statements:

1. As we all know, a differential will always send torque toward the path of least resistance. If the left rear wheel has the best traction, the differential will spin the right one. Now.... please understand this next part when making any argument: whether rolling or not, the side opposite from the power maintines friction contact, giving the vehicle lateral stability. I have been astounded in the last few weeks at the number of people that do not understand this basic fact. A quad has no way of performing this function in the absence of the differential. It always tries to put torque to both wheels, and if the surface is slippery enough, both will slip. This causes the vehicle to instantly move sideways on any kind of camber, and you go right into the ditch (if you are lucky).
2. Because the quad always tries to put torque down to both wheels, it does quite well when emulating LS up until the surface gets too slick. Then it falls on its face because of #1.
3. With no connecting bar between the wheels, a quad tries to emulate a locked axle by applying torque and limiting wheel spin. Does this sound to anybody a lot like LS? It should, because it is. In low speed situations such as rock crawling, there is a lot of flailing that goes on. Another major drawback is the fact that unlike a locked diff, the vehicle can never apply 100% of the torque meant for the left wheel to the right. This does not look like a big deal on paper, because the motors are so powerful, right? Well, in the mountains with a 7,000lb+ truck, those single wheel motors can get overwhelmed pretty quick.

Those are the "whys", I will close this with the "whats"... what happened when the vehicle hit the real world.

I have a long, steep mountain driveway that gets plenty of snow and ice. There are off-camber sections, and sections where the drop into the Rogue River is over 1,000 feet. It is of great importance to stay on the road.

On an icy day, I can drive up in a bone-stock F250 and even when there is some slip/sliding, it will perform the way all of us are used to 4x4 vehicles handling. There is rock under the ice & snow, and sometimes there is some spinning to get grip.

Trying to do the same route in the quad-motored rig with equal tires is a terrifying, death-defying feat. The truck tries to put torque to all wheels, giving it zero lateral stability when they all break free at the same time. The truck lurches sideways at completely inappropriate times; it is like Bambi on ice... all four legs going their own way. I was lucky to only end up in the ditch, and I learned very fast to leave that truck parked if it was slick, taking instead the Ford or the Tesla.

Kind of defeats to purpose of a 4x4 rig, right? Granted, this problem really only presents in very slippery conditions, but since those are the conditions in which I live, my future purchases will have a differential front & rear. No more quads for this guy!

 

[KElkhorn]

I started out on the "other" side of this argument, but got schooled by the real world. For the purposes of this discussion, I will be just talking about the quad-motor design, but the Tri-motor (Hummer, Tesla) will have the same limitations on any axle with two motors.

Let's start with with my new position on the matter; The quad motor design is at a significant disadvantage when compared to a vehicle with differentials on certain low traction surfaces.

I got a lot of blow-back on this topic on other forums, mostly from people who were not even driving the truck. Weird. I am certainly open to discussion on the topic, that is what these forums are for, but please... please have a very good operational knowledge of "rolling friction" and the torque vectoring characteristics of the differential when joining the conversation. "No, you are wrong" is not an informed position.

Let's start by establishing the three modes a differential can be used in:

1. Open
2. Limited Slip
3. Locked

Next let's establish that a quad has no differential, so it must emulate these modes to address different traction needs.

1. A quad has no way to effectively emulate an open differential. It always tries to apply torque to both sides.
2. A quad is relatively good at emulating the Limited Slip mode. In fact, it is what it is best at.
3. A quad has no way of fully umulating fully locked mode

Now to explain those three statements:

1. As we all know, a differential will always send torque toward the path of least resistance. If the left rear wheel has the best traction, the differential will spin the right one. Now.... please understand this next part when making any argument: whether rolling or not, the side opposite from the power maintines friction contact, giving the vehicle lateral stability. I have been astounded in the last few weeks at the number of people that do not understand this basic fact. A quad has no way of performing this function in the absence of the differential. It always tries to put torque to both wheels, and if the surface is slippery enough, both will slip. This causes the vehicle to instantly move sideways on any kind of camber, and you go right into the ditch (if you are lucky).
2. Because the quad always tries to put torque down to both wheels, it does quite well when emulating LS up until the surface gets too slick. Then it falls on its face because of #1.
3. With no connecting bar between the wheels, a quad tries to emulate a locked axle by applying torque and limiting wheel spin. Does this sound to anybody a lot like LS? It should, because it is. In low speed situations such as rock crawling, there is a lot of flailing that goes on. Another major drawback is the fact that unlike a locked diff, the vehicle can never apply 100% of the torque meant for the left wheel to the right. This does not look like a big deal on paper, because the motors are so powerful, right? Well, in the mountains with a 7,000lb+ truck, those single wheel motors can get overwhelmed pretty quick.

Those are the "whys", I will close this with the "whats"... what happened when the vehicle hit the real world.

I have a long, steep mountain driveway that gets plenty of snow and ice. There are off-camber sections, and sections where the drop into the Rogue River is over 1,000 feet. It is of great importance to stay on the road.

On an icy day, I can drive up in a bone-stock F250 and even when there is some slip/sliding, it will perform the way all of us are used to 4x4 vehicles handling. There is rock under the ice & snow, and sometimes there is some spinning to get grip.

Trying to do the same route in the quad-motored rig with equal tires is a terrifying, death-defying feat. The truck tries to put torque to all wheels, giving it zero lateral stability when they all break free at the same time. The truck lurches sideways at completely inappropriate times; it is like Bambi on ice... all four legs going their own way. I was lucky to only end up in the ditch, and I learned very fast to leave that truck parked if it was slick, taking instead the Ford or the Tesla.

Kind of defeats to purpose of a 4x4 rig, right? Granted, this problem really only presents in very slippery conditions, but since those are the conditions in which I live, my future purchases will have a differential front & rear. No more quads for this guy!

No you are wrong.

Had to do it.

 

[R.I.P.]

No you are wrong.

Had to do it.

🤦‍♂️

 

[R.I.P.]

Thank you for getting that out of the way... 😁

 

[KElkhorn]

In all seriousness, great information, count me as one of those who thought quad motors would be a distinct advantage and overlooked these scenarios.

So really it comes down to the ability to maybe potentially some day be able to tank steer as a party trick, or the ability to safely drive your vehicle in most conditions.

 

[Wiseguy]

I started out on the "other" side of this argument, but got schooled by the real world. For the purposes of this discussion, I will be just talking about the quad-motor design, but the Tri-motor (Hummer, Tesla) will have the same limitations on any axle with two motors.

Let's start with with my new position on the matter; The quad motor design is at a significant disadvantage when compared to a vehicle with differentials on certain low traction surfaces.

I got a lot of blow-back on this topic on other forums, mostly from people who were not even driving the truck. Weird. I am certainly open to discussion on the topic, that is what these forums are for, but please... please have a very good operational knowledge of "rolling friction" and the torque vectoring characteristics of the differential when joining the conversation. "No, you are wrong" is not an informed position.

Let's start by establishing the three modes a differential can be used in:

1. Open
2. Limited Slip
3. Locked

Next let's establish that a quad has no differential, so it must emulate these modes to address different traction needs.

1. A quad has no way to effectively emulate an open differential. It always tries to apply torque to both sides.
2. A quad is relatively good at emulating the Limited Slip mode. In fact, it is what it is best at.
3. A quad has no way of fully umulating fully locked mode

Now to explain those three statements:

1. As we all know, a differential will always send torque toward the path of least resistance. If the left rear wheel has the best traction, the differential will spin the right one. Now.... please understand this next part when making any argument: whether rolling or not, the side opposite from the power maintines friction contact, giving the vehicle lateral stability. I have been astounded in the last few weeks at the number of people that do not understand this basic fact. A quad has no way of performing this function in the absence of the differential. It always tries to put torque to both wheels, and if the surface is slippery enough, both will slip. This causes the vehicle to instantly move sideways on any kind of camber, and you go right into the ditch (if you are lucky).
2. Because the quad always tries to put torque down to both wheels, it does quite well when emulating LS up until the surface gets too slick. Then it falls on its face because of #1.
3. With no connecting bar between the wheels, a quad tries to emulate a locked axle by applying torque and limiting wheel spin. Does this sound to anybody a lot like LS? It should, because it is. In low speed situations such as rock crawling, there is a lot of flailing that goes on. Another major drawback is the fact that unlike a locked diff, the vehicle can never apply 100% of the torque meant for the left wheel to the right. This does not look like a big deal on paper, because the motors are so powerful, right? Well, in the mountains with a 7,000lb+ truck, those single wheel motors can get overwhelmed pretty quick.

Those are the "whys", I will close this with the "whats"... what happened when the vehicle hit the real world.

I have a long, steep mountain driveway that gets plenty of snow and ice. There are off-camber sections, and sections where the drop into the Rogue River is over 1,000 feet. It is of great importance to stay on the road.

On an icy day, I can drive up in a bone-stock F250 and even when there is some slip/sliding, it will perform the way all of us are used to 4x4 vehicles handling. There is rock under the ice & snow, and sometimes there is some spinning to get grip.

Trying to do the same route in the quad-motored rig with equal tires is a terrifying, death-defying feat. The truck tries to put torque to all wheels, giving it zero lateral stability when they all break free at the same time. The truck lurches sideways at completely inappropriate times; it is like Bambi on ice... all four legs going their own way. I was lucky to only end up in the ditch, and I learned very fast to leave that truck parked if it was slick, taking instead the Ford or the Tesla.

Kind of defeats to purpose of a 4x4 rig, right? Granted, this problem really only presents in very slippery conditions, but since those are the conditions in which I live, my future purchases will have a differential front & rear. No more quads for this guy!

Great write up! I had no idea what that “lock rear differential” button did, but you cleared it up! If I’m going to the Poconos in PA to ski in the mountains in the winter, be sure to use that option driving in the ice and snow on the mountainous roads

 

[R.I.P.]

Great write up! I had no idea what that “lock rear differential” button did, but you cleared it up! If I’m going to the Poconos in PA to ski in the mountains in the winter, be sure to use that option driving in the ice and snow on the mountainous roads

Um, no lol. You do not want to lock your diff in snow & ice, you want the diff vectoring torque to keep the truck straight. Locking the diff can have the effect of kicking your rear end out, because it can break both tires lose at the same time.

Your best mode for snow & ice is likely "normal" mode.
👍

 

[Wiseguy]

Um, no lol. You do not want to lock your diff in snow & ice, you want the diff vectoring torque to keep the truck straight. Locking the diff can have the effect of kicking your rear end out, because it can break both tires lose at the same time.

Your best mode for snow & ice is likely "normal" mode.
👍

Wait I just realized if I locked it then I’d be doing close to the same thing you are saying NOT to do haha so in that case, when would I lock my rear differential?

 

[R.I.P.]

Wait I just realized if I locked it then I’d be doing close to the same thing you are saying NOT to do haha so in that case, when would I lock my rear differential?

It truly is not very often that you need to lock the rear diff, especially since Ford's traction control is actually quite good.

One area where I would definitely lock it would be in lets say a creek crossing, where boulders are slippery and moving. By keeping both Wheels moving forward at the same rate it will maximize forward push while preventing one from spinning to wildly and digging holes.

Likewise, on level ground that may be very slippery it can provide extra push forward. However, anytime you are on a camber or a slope, both Wheels spinning at the same time can cause the vehicle to move sideways instead of forward.

A third use for the locking diff would be crawling over rock. locking the diff will keep spin in the rear to a minimum, and both wheels turning at the same speed.

 

[Wiseguy]

It truly is not very often that you need to lock the rear diff, especially since Ford's traction control is actually quite good.

One area where I would definitely lock it would be in lets say a creek crossing, where boulders are slippery and moving. By keeping both Wheels moving forward at the same rate it will maximize forward push while preventing one from spinning to wildly and digging holes.

Likewise, on level ground that may be very slippery it can provide extra push forward. However, anytime you are on a camber or a slope, both Wheels spinning at the same time can cause the vehicle to move sideways instead of forward.

A third use for the locking diff would be crawling over rock. locking the diff will keep spin in the rear to a minimum, and both wheels turning at the same speed.

Thank you for the very detailed response! Sounds like I won’t be using it very frequently unless I venture into the wilderness more frequently

 

[eRockBoon]

This is great! I think engineering explained made a similar point in a YouTube video on the quad motor Rivian. But it also praises all of the other strengths of the quad motor.

I love knowing I can get all 375 ft lbs of torque to the wheel with traction in my lightning and a quad motor Rivian is stuck at 250 ft lbs. although the new enduro motors for the two motor Rivian will provide over 400 ft lbs. I am excited to see how those do in the wild. But I will still likely cancel my Rivian reservation. Not excited about paying $25,000 to swap my ER Pro over to a R1T-duo.

 

[R.I.P.]

This is great! I think engineering explained made a similar point in a YouTube video on the quad motor Rivian. But it also praises all of the other strengths of the quad motor.

I love knowing I can get all 375 ft lbs of torque to the wheel with traction in my lightning and a quad motor Rivian is stuck at 250 ft lbs. although the new enduro motors for the two motor Rivian will provide over 400 ft lbs. I am excited to see how those do in the wild. But I will still likely cancel my Rivian reservation. Not excited about paying $25,000 to swap my ER Pro over to a R1T-duo.

The dual-motor Rivian is going to be the better truck. Lighter, more efficient, and twin differentials for better traction.

It will be slower 0-60... A little bit. So for those that think that is important, the quad is still the better choice.

 

[Henry Ford]

RIP, if I recall you haven't bought a Lightning yet? Have you driven one?

I mentioned it on another thread but it is easily the best handling vehicle I've ever driven in snow. If driven carefully - the only way to drive in slippery conditions - it's incredible. I did turn the traction control off to do some donuts, that's about as out of control as I've had it. Of course the hills of southern Michigan are slightly different than the "hills" of the west.

 

[R.I.P.]

RIP, if I recall you haven't bought a Lightning yet? Have you driven one?

I mentioned it on another thread but it is easily the best handling vehicle I've ever driven in snow. If driven carefully - the only way to drive in slippery conditions - it's incredible. I did turn the traction control off to do some donuts, that's about as out of control as I've had it. Of course the hills of southern Michigan are slightly different than the "hills" of the west.

Yes, I was given one for 2 weeks for an evaluation. There is a company in California working on an exciting upgrade that let me have thiers.

I was very impressed, and I agree that the handling and traction lived up to my expectations; which were very high.
😎👍

 

[eRockBoon]

Yes, I was given one for 2 weeks for an evaluation. There is a company in California working on an exciting upgrade that let me have thiers.

Ooohh tell me more! Also, what did you do with your Rivian?

 

[ChasingCoral]

It truly is not very often that you need to lock the rear diff, especially since Ford's traction control is actually quite good.

One area where I would definitely lock it would be in lets say a creek crossing, where boulders are slippery and moving. By keeping both Wheels moving forward at the same rate it will maximize forward push while preventing one from spinning to wildly and digging holes.

Likewise, on level ground that may be very slippery it can provide extra push forward. However, anytime you are on a camber or a slope, both Wheels spinning at the same time can cause the vehicle to move sideways instead of forward.

A third use for the locking diff would be crawling over rock. locking the diff will keep spin in the rear to a minimum, and both wheels turning at the same speed.

Wouldn’t another be when trying to get loose from or to plow through mud or snow. Locking the differential would keep applying power at the rate needed for the wheel with the most resistance rather than spinning at the rate the low resistance wheel would allow.

 

[R.I.P.]

Wouldn’t another be when trying to get loose from or to plow through mud or snow. Locking the differential would keep applying power at the rate needed for the wheel with the most resistance rather than spinning at the rate the low resistance wheel would allow.

Typically, this is going to introduce lateral motion which is not helpful in very slippery situations. Ford's traction control is actually extremely good, making it much more effective to not lock the differential; letting the traction control try to get you some forward motion while not losing your lateral stability.

Experimenting is learning, so experiment with your truck to get a feel for how it reacts in these situations.

 

[R.I.P.]

Ooohh tell me more! Also, what did you do with your Rivian?

Sold the Rivian, and unfortunately it is not my place to talk about the Lightning project. I get to be a fly-on-the-wall for exciting EV projects still, but that would likely end if I talked about them out of turn.
😎

 

[KElkhorn]

Since this seems to be somewhat of an AMA for Sean. . . . .

To me it seems like modular replacable pack design is both good and bad for aftermarket/battery upgrades. Good in that a similar voltage/capacity battery should be fairly easy to plug and play, bad in that it would potentially result in many more connection points, both mechanical and electrical in the even that replacement batteries have significantly improved capacity, etc. What are your thoughts on this? I think I'm on the same page with you if I read some of your other posts correctly that I'm fully relying on my battery having problems, and was on day 1 when I placed my reservation, but having most of those within the 8 year 100K warranty period where I either go through a few batteries on my way to 100K miles and trade it in, or Ford does what others have and truly resolves the problems under warranty/recall as GM has done. One of the reasons I drug my feet a bit on the Rivian but signed up immediately for the Ford (as well as the silverado I reserved 2 after my experience with limited availability of the Lighting)

This may admittedly be a lazy question, but even if I researched a bit more I'd probably still be interested in what you had to say. My understanding of BMS systems is fairly limited, I'm curious how they actually keep track of battery capacity, or in other terms, if I have the ER battery which let's assume has the published usable capacity of 131 kWh. If I constantly charge to 90% (as opposed to 100%), and don't ever discharge below 30%, is there potential for drift? I suppose another way of asking this would be how much variation do you think there would be in a battery that reads 90%, do you think that really means 118 kWh +/- 1kWh or +/-5kWh, and how well does this hold up over time?

 

[R.I.P.]

Since this seems to be somewhat of an AMA for Sean. . . . .

To me it seems like modular replacable pack design is both good and bad for aftermarket/battery upgrades. Good in that a similar voltage/capacity battery should be fairly easy to plug and play, bad in that it would potentially result in many more connection points, both mechanical and electrical in the even that replacement batteries have significantly improved capacity, etc. What are your thoughts on this? I think I'm on the same page with you if I read some of your other posts correctly that I'm fully relying on my battery having problems, and was on day 1 when I placed my reservation, but having most of those within the 8 year 100K warranty period where I either go through a few batteries on my way to 100K miles and trade it in, or Ford does what others have and truly resolves the problems under warranty/recall as GM has done. One of the reasons I drug my feet a bit on the Rivian but signed up immediately for the Ford (as well as the silverado I reserved 2 after my experience with limited availability of the Lighting)

This may admittedly be a lazy question, but even if I researched a bit more I'd probably still be interested in what you had to say. My understanding of BMS systems is fairly limited, I'm curious how they actually keep track of battery capacity, or in other terms, if I have the ER battery which let's assume has the published usable capacity of 131 kWh. If I constantly charge to 90% (as opposed to 100%), and don't ever discharge below 30%, is there potential for drift? I suppose another way of asking this would be how much variation do you think there would be in a battery that reads 90%, do you think that really means 118 kWh +/- 1kWh or +/-5kWh, and how well does this hold up over time?

Drift: Yes, the BMS's accuracy will drift over time. If you are counting your electrons very carefully, it should be minimal, but it will certainly happen.

It is a good idea to allow a full charge every couple of months or so just to zero that out, depending on how much you use the vehicle.