Likely referring to the MTS modes. What happens in hill decent when both front wheels are locked together etc., It cant control wheels independently. Maybe there will be unexpected consequences. One way to find out!
LC250 CV joints - Should I consider upgrading
- Thread starter G0ebs
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I don't have all the modes, only ATRAC which functions flawlessly. I've never been at a 'loss for traction' in the rear where a front locker would do anything for me that ATRAC wasn't already doing, even driving up very wild 30+° inclines in rutted out mud / clay / dry earth. I'm normally aired down, 18-20 psi to start. Only time I've cut off ATRAC was in the dunes, where the traction control was killing power where I needed it.
I'm not sure how strong the front differential is when owners start building it like a Jeep, the CV's on most Toyotas are built out of glass. Doesn't matter the model. They are a very, very common failure point - and the next would be the front differential. The 79's also commonly break axles as well, just less common than the CV's.
Closest I've been to being in your claimed position was a water crossing in Utah, where I had 2nd gear / 4L / rear locked and pinned to the floor for a solid 10-seconds, nearly getting bogged to the chassis. I don't make it a habit of trying to test the limits of the cruiser in incredibly remote areas.
As I mentioned I'm use to various situation with lockers. I usually reserve the front lockers for genuine traction loss scenarios. As the Swiss Army chauffeur pocket guide notes in its Off-Road Techniques chapter "Procedures for engaging 4x4, diff locks, and low range" binding the front left and right wheels together during a descent is a bad idea. Because you will kill first your steering feel.
Last generation Toyota 4Runner & Tacoma w/ 4.0L V6 came up as a comparison (in a different post) being implied as better off road & easier on CV shafts than the new frail Land Cruiser, & that may or may not prove to be true.
I see them as apple to oranges comparing a mechanical 4WD system to an advanced AWD system. Biggest factor to me is applied torque when the CV joint breaks. A 2023 Toyota 4R mechanical 4WD driveline had 278 lb.ft. of torque to deal with, where the AWD LC (& hybrid 4Runners & Tacos) have up to 475 lb.ft. of torque being applied… an enormous improvement. That’s a lot more stress on the driveline.
To put in perspective -my 1997 7.3L PSD F250 (that has towed anything I’ve given it) when new only made 225HP & 450 lb.ft.of torque. We all hope Toyota beefed up everything to handle that increase w/ the big power upgrade. Pretty big question right now. Using AWD is just not the same as jumping out & locking the hubs as we did a few years ago. And when we did, we had to be very careful if we’d modified the power available. My old K5 Blazer it was always driveshaft u-joints giving up first.
Electronics are now necessary to use all of the torque & power. Spinning a wheel & then locking it up on a rock or something is going to break at these torque amounts. Let the electronics (4Lo, MTS, Crawl) keep you whole.
I see them as apple to oranges comparing a mechanical 4WD system to an advanced AWD system. Biggest factor to me is applied torque when the CV joint breaks. A 2023 Toyota 4R mechanical 4WD driveline had 278 lb.ft. of torque to deal with, where the AWD LC (& hybrid 4Runners & Tacos) have up to 475 lb.ft. of torque being applied… an enormous improvement. That’s a lot more stress on the driveline.
To put in perspective -my 1997 7.3L PSD F250 (that has towed anything I’ve given it) when new only made 225HP & 450 lb.ft.of torque. We all hope Toyota beefed up everything to handle that increase w/ the big power upgrade. Pretty big question right now. Using AWD is just not the same as jumping out & locking the hubs as we did a few years ago. And when we did, we had to be very careful if we’d modified the power available. My old K5 Blazer it was always driveshaft u-joints giving up first.
Electronics are now necessary to use all of the torque & power. Spinning a wheel & then locking it up on a rock or something is going to break at these torque amounts. Let the electronics (4Lo, MTS, Crawl) keep you whole.
Yeah I don’t know the answer yet to how it affects MTS. Might get wonky. And you make really great points about increased risk of failures, no doubt about it.
I appreciate your knowledge and sensibility!
My initial thought on ATRAC/MTS when fully locked, is all wheels are going to be spinning at the same speed (ignoring drivetrain play), and the traction control system will think everything is fine and it doesn't need to do anything.
The system only knows to activate based on speed differential between any of the four wheels.
It's an advanced system, so maybe if you're turning and it knows it should see a speed diferential becuase of that, but it doens't, then I guess it could have an issue? Or if you're spinning all four wheels, but an accelerometer tells the system it's not moving.
Could go either way I guess.
The system only knows to activate based on speed differential between any of the four wheels.
It's an advanced system, so maybe if you're turning and it knows it should see a speed diferential becuase of that, but it doens't, then I guess it could have an issue? Or if you're spinning all four wheels, but an accelerometer tells the system it's not moving.
Could go either way I guess.
The various terrain settings, you can basically auto pilot the drive modes.
To me, watching the part of the video where the CV broke a few times, it looks like it was ATRAC that broke it. He said he put it in 4 lo so would assume that was ATRAC that was governing front wheels. And it looked like ATRAC wheel behavior, per my experience (on a 1958, which doesn't have MTS of course).
So my thinking is that either
1) Toyota messed up here with ATRAC, possibly because ATRAC hasn't been used with these new vehicles that have so much more torque than past, or
2) there was a prior issue with CV that came from manufacturing, keeping in mind that this was a First Edition, so relatively early off the line, or
3) there was a prior issue with CV because, well, that's a weak point with all these Toyotas when you use them hard.
I would think that if it's 1), then we'd be seeing a lot more failures, or will see a lot more failures over next couple years.
I think time will give us a lot more information here. My guess is that it's 2) or 3).
But given that Toyota CVs, even those in 70 series, tend to break under hard use, I think it just makes sense to carry extra CVs if you are going to be very remote and/or doing hardish wheeling. Which is of course a fraction of a percent of 250 owners, but maybe a number of folks on this board. But even for that small number of folks who do that with their 250s, I'd guess they only do that for a small percent of the time.
So personally, like I said before, when I do a lift, rather than just buy another set of 250 CVs to carry as extras, I'll be buying and installing those Tacoma/ 4runner CVs, and carrying the original 250 CVs as extras.
I definitely don't think that this video, on its own, is an indication that the 250 is somehow weaker or more fragile than other vehicles with the Land Cruiser badge, nor should it cause most people to worry about their CVs.
So my thinking is that either
1) Toyota messed up here with ATRAC, possibly because ATRAC hasn't been used with these new vehicles that have so much more torque than past, or
2) there was a prior issue with CV that came from manufacturing, keeping in mind that this was a First Edition, so relatively early off the line, or
3) there was a prior issue with CV because, well, that's a weak point with all these Toyotas when you use them hard.
I would think that if it's 1), then we'd be seeing a lot more failures, or will see a lot more failures over next couple years.
I think time will give us a lot more information here. My guess is that it's 2) or 3).
But given that Toyota CVs, even those in 70 series, tend to break under hard use, I think it just makes sense to carry extra CVs if you are going to be very remote and/or doing hardish wheeling. Which is of course a fraction of a percent of 250 owners, but maybe a number of folks on this board. But even for that small number of folks who do that with their 250s, I'd guess they only do that for a small percent of the time.
So personally, like I said before, when I do a lift, rather than just buy another set of 250 CVs to carry as extras, I'll be buying and installing those Tacoma/ 4runner CVs, and carrying the original 250 CVs as extras.
I definitely don't think that this video, on its own, is an indication that the 250 is somehow weaker or more fragile than other vehicles with the Land Cruiser badge, nor should it cause most people to worry about their CVs.
I've never seen the solid axle burfield joint fail at the joint, those are quite stout. Instead they either snap the shaft in two or break at the splines, both can be improved by going to fine spline and chromoly which are known to cause 3rd members to break when wheeled hard. IMO best solution on the solid axle fronts is to do a part-time conversion which will move the failure point to the free wheel hub 99% of the time which is a quick, clean, easy trail fix for the least amount of money.
Still question condition of that CV joint. Had a few vehicles where cv boot tore& when you get moisture in them picks up dirt & the grease turns from blue- grey to brown. That joint tolerance excepts no dirt & begins eating itself. Put a worn cv under stress & it WILL break.
The video explained he had already 30,000 miles on the rig b4 the testing. Since he is a tester, God only knows what kind of stressors he may have exposed that rig to?? As others point out, it appears the break occurs from a certain condition where a break point can happen when a spin meets a hard place.
For a pre existing (worn) CV joint, failure will occur with extreme pressure.
For a pre existing (worn) CV joint, failure will occur with extreme pressure.
It's a multifactor situation:
-Tire pressure. Road pressure is wrong for unpaved, low-speed tracks should've been aired down.
-Test bias. The journalist is testing tires on that specific slope, and stumbles onto the fact that a bad-looking road tire tracks just as well as an aggressive, good-looking off-road tire.
-Driver skill. When traction breaks, the worst response is to add power even with A-TRAC active.
Because he was testing tires, the driver induced high wheel spin in a high-torque situation with over-pressurized tires. That combination sent heavy vibration through the drivetrain and snapped a tripod joint. Pretty common failure mode, honestly.
What would a Swiss driver do in that situation? There are 3 types of grip in tire science, molecular adhesion, hysteresis and mechanical grip. The only way to boost the mecanical grip is to use snow chains because even the most aggressive mud terrain will not bite like chains.
In a genuine low-traction situation, I'd lower tire pressure, engage a locker to cut drivetrain vibration, go slow, and stop the moment traction is lost. Then find another line rather than fight it or mount chains.
im also in this boat.
If you look at the picture Ryan posted, @30k miles the grease looks to have lost viscosity, the tripod joint looks brown and oxidized, grease looks discolored.
I'm going to be inspecting my boots every oil change (4k miles)
EDIT: I will be going with Tacoma CVS and carrying the OEM as spares, Perhaps under the vehicle in the empty space where the gas tank should have filled
Following up on the broken CV joint discussion, the journalist made an interesting point I hadn't considered before: when a tripod joint fails, it tends to fling its broken parts "away" and they never bind back up, which checks out with what I've seen. That's not necessarily the case with a DOJ (double offset joint) even though it's never happened to me or anyone I know personally, apparently when one of those fails, it may end up binding, leaving you stuck in the middle of nowhere.
The only time I've had a joint come completely apart was a Rzeppa. It sounded like and explosion but it wasn't actually broken into pieces. It came out from a combination of high peak torque and suspension geometry causing extreme distortion under load, which just popped it apart rather than shattering it
Here is my comments. First, there's a common misconception between Rzeppa joints and double offset joints. Both use a ball-and-cage design (which is why they get loosely lumped together as "CV joints"), but a Rzeppa joint is built for high articulation angles with no plunge, while a double offset joint is built for plunge with a more limited angle. They're not interchangeable, each is engineered for its specific position in the driveline. You'll typically find a Rzeppa joint outboard, and a tripod or DOJ inboard.
In my (admittedly limited) experience, I've seen plenty of tripod joints fail, unlike ball-and-cage designs. What usually fails next is the axle itself, typically at the slotted (plunging) section.
Ball-and-cage designs are less rugged than tripod joints overall; their main advantage is smoother torque transmission with less vibration.
Then IMHO the driver made a mistake here. He used Crawl Control going uphill, but then disengaged it and backed down using the brakes instead. That's a bad move, and it can easily lead to a total loss of vehicle control.
The only time I've had a joint come completely apart was a Rzeppa. It sounded like and explosion but it wasn't actually broken into pieces. It came out from a combination of high peak torque and suspension geometry causing extreme distortion under load, which just popped it apart rather than shattering it
Here is my comments. First, there's a common misconception between Rzeppa joints and double offset joints. Both use a ball-and-cage design (which is why they get loosely lumped together as "CV joints"), but a Rzeppa joint is built for high articulation angles with no plunge, while a double offset joint is built for plunge with a more limited angle. They're not interchangeable, each is engineered for its specific position in the driveline. You'll typically find a Rzeppa joint outboard, and a tripod or DOJ inboard.
In my (admittedly limited) experience, I've seen plenty of tripod joints fail, unlike ball-and-cage designs. What usually fails next is the axle itself, typically at the slotted (plunging) section.
Ball-and-cage designs are less rugged than tripod joints overall; their main advantage is smoother torque transmission with less vibration.
Then IMHO the driver made a mistake here. He used Crawl Control going uphill, but then disengaged it and backed down using the brakes instead. That's a bad move, and it can easily lead to a total loss of vehicle control.
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Kind of lost me here. What are you suggesting he should have done?
I don't think Crawl of DAC work in reverse? I haven't tried it though.
It does but because of how it pulses the brakes, you’re doing constant little lurches. Having used it while reversing down a very steep and sketchy decline, I prefer my foot!
Use the same strategy as up hill, use crawl control mode down hill.
Also in when using crawl control mode, no need to lock the rear differential let the computer work for you on all 4 wheels. Just lock the center diff, Crawl Control only has to manage power side to side on each axle, rather than trying to juggle distribution across all four wheels, it works more predictably and effectively.
Locking rear or front differential force both wheels on that axle to spin at the same speed, so any time they need to travel different distances, turning or one wheel riding up/down over uneven ground, the tire has to scrub instead. That scrub kills momentum right when traction is already marginal.
A-TRAC avoids this by leaving the diff (rear or fornt) open and just braking the slipping wheel, letting the other wheel spin at its own natural speed while still getting power. No forced scrub, but power still goes where it's needed which is why it often beats a locker rather than being a downgrade from one.
A locker still wins when a wheel has zero grip (fully unloaded, on ice) there's no slip for A-TRAC to brake against, so forcing both wheels together is the only way to keep driving.
That's why the rule of thumb holds: leave it open by default, lock only for a specific situation.
Have you used crawl control reversing down a very steep decline like this? How was your experience compared to just managing the brakes yourself?
My opinion is he definitely made the smart choice.
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