4runner Off-Road vs Landcruiser 1958: Axles and front suspension

The local dealer had a 6th gen 4runner OR and several LC 1958s on the lot, so I stopped by for a look.

I was curious about the front CV axles on the 4r OR trim. Specifically because the Tacoma ORs supposedly have upgraded high-angle CV axles in the front, and a larger rear axle than the Tacoma SR5. This screen cap from a tinkerer’s adventure video shows the difference in CV axles:
I wanted to see if these differences hold true on 4runners.

Below are some pics of the 4r OR.

4Runner Off-Road

Unfortunately, it looks like they are the plain jane regular CV axles…nothing special (but someone correct me if I’m wrong).

Worth noting is that the front shock lower mount is indeed a single shear arrangement (I previously had seen Pre-production pictures with either a double shear or a single shear arrangement, so I wasn’t sure what they settled on).

What wasn’t a surprise is a lack of a frame mounted bump-stop. It’s all done virtually by abusing the shock and shock-tower (sorry for the editorial ).
LCA-front

LCA-back

Brightened and zoomed in CV detail:



The 4r OR rear axle:



I wish there was a 4runner SR5 to compare the axles…so unfortunately I still can’t conclude if the SR5 and OR trims have any substantial driveline differences like the Tacomas. Does anyone know which rear axle is on the OR from the part number sticker?

While there weren’t any SR5 4runners, there were plenty of 1958s on the lot. Might as well take a look, see below.


LC250 1958
The 1958 trim looks like it has a similar CV axle to the 4R OR, so nothing special here. It also has the same single shear lower shock mount. But the LC has the frame mounted bump stop, which appears to be a bolt on part.
(The 4runner pics shows holes covered by a plastic plug in this spot, but unsure if they are threaded holes which accept the LC bump-stops).

LCA-front

LCA-back



The 1958 rear axle:


Laser etched ID…fancy! Anybody know how this rear axle compares to the 4R OR pictured above?

 

Does it work? There were reports of Tacos snapping front shock top hat doing mild offroading. I have not heard about any changes in 4Runner from that setup.

 

I’d guess the tophat situation (fusible link) is the same on the 4runners, but not sure to tell you the truth. Here’s a pic of what the OR on the lot had..

 

edit: Hmm, maybe the 4R OR does NOT have the breakable top hat.

I found the ICON video where they broke the Tacoma tophat. This is a screengrab of the side that didn’t break.
The silver plate on top is what breaks (under his index finger, in shadow).

The 4runner seems to be different, it looks like a normal steel dome on top. That’s probably a good thing. On the other hand, the “internal bumpstop valving” on tacoma shocks was a very sudden and sharp increase in compression damping. If there is no fuse, that strong hydraulic hammering that happens whenever the shock compresses over bumps may just lead to fatigue cracking of the frame where the shock mounts up…or failure of the single shear bolt mount on the LCA. Apparently, on Tacomas it doesn’t take that much suspension travel to hit the “bump-stop valving” range, which means that the hydraulic hammering impacts would happen frequently in normal road conditions.

I’m curious to see if it’s possible to install the LC’s frame mounted bump stop. But I think it’s going to take a new 6th gen owner to see if plugs covering the holes in the frame are threaded.

 

I will say, it really seems like all these unexpected differences make it hard to know what you’re gonna get.

For example, I was hoping that maybe the 6th gen 4R would end up with double shear lower shock mounts on the lower control arms, because I noticed that at least some production 4th gen Tacomas had them (besides seeing them on early 4runner press vehicles). This is what the LCA looks like on the stock 4th gen Tacoma in the ICON video. You can see it has an added bracket welded on the lower shock mount to make it double shear. This design allows the bolt to take shear loads perpendicular to the bolt, which eliminates any bending forces (on the bolt and LCA mount) that could happen on a single shear arrangement.

It’s apparent it also has the high-angle CV axle (the hub side and the inner boot “stepped cone” shape is different).

I thought the new “Landoma 4Cruiser” architecture was all about parts sharing. Apparently not. It’s more like a box of chocolates instead!

 

No bump stop and the single shear bolt seems like a bad combination. Should we take bets on how long it takes for a recall to come out for it?

 

So the 4Runner get a traditional steel top hat with the Bilsteins, like I predicted in July.

 

Does that mean it will just snap the bottom bolt instead?

 

Go figure. Makes you wonder why they felt a need to make the breakable top hat to begin with. There had to be a reason, since it’s way too “designed” for the idea to be a simple mistake.

 

The shock bushing rides on a large-diameter spigot welded to the LCA, a bit like the 5th gen's rear shocks. The bolt doesn't take shear loads.

 

The manufacturing quality of the potmetal top hat used in Tacomas was really poor. Maybe the supplier was experimenting with metal injection molding (MIM):

 

Time will tell. It seems to be a such a questionable way to mount a coilover shock. Not only does it hold up to the weight of the car, but also will have to absorb cyclic hydraulic hammering impacts from the bump-stop valving zone. Not to mention the physical stop when the shock body hits the physical stop against the top hat. I doubt a steel top hat would yield, so that lower mount looks more and more like the weakest link.

I’ll make a prediction myself…4runners will be getting the LCAs with the double shear lower shock mount in short order. Maybe even before the first 4runner breaks a coilover clean off of an LCA. After all, it’s not a good look to see a 4runner flat on its chin after the front falls off. It wouldn’t be like a top hat failure on the Tacoma where the front is still held up by the coils.

 

Are you sure about that? The rear shock lower mount is only taking damping loads, and no weight. The weight of the vehicle itself is taken by the separate coil and the upper and lower coil-seats on the rear axle and the frame.

But the front coilover lower bolt takes both damping forces and the weight of the vehicle. The coilover transmits both forces through the top hat and the lower single shear mount. Unless I’m more confused than ever.

 

But then why make it a two piece design with such a tiny interfacing area around the very edges of that disc.

On first sight, that part looks purpose-built to predictably break at a certain load.

 

The lower spigot takes the shear loads (though the loads are obviously higher with the front coilover shock). The bolt is simply there to prevent the shock bushing from sliding off the spigot.

If the bolt rattles itself loose, the shock bushing can slide off the spigot. Happened with this Land Cruiser:

 

That’s better than just a bolt but at some point when the internal dampening and bump stops fail something will need to give and it will be either that sleeve or top hat. It’s such a simple thing to stop with just a basic bump stop like we’ve always had.

 

I am sure, they are in the bean counter room hoping that 4R owners treat their vehicles more like Highlander owners and never take it off the road or hit pot holes ect ect.
I think the days are long gone of them building a vehicle that will take anything you throw at it.

 

Fair enough point that it’s the “spigot” tube taking the loads, not the bolt. I’m sure they did some engineering analysis of how that shock loads affect the spigot, but for sure that spigot has got to be experiencing some sort of bending loads given the fact it’s cantilevered. I have to wonder if it also introduces torsional loads/movement on the lower control arm itself.

The failure of the LC you linked is very interesting. I think it shows that failure of this mounting scheme doesn’t have to be a broken spigot sheared off at the weld, failures could be a lot less predicable. Looking at the video, I’m not totally sure, but it almost looks like the bolt hole is ovalled out. It’s a possibility bending forces on the spigot end up stretching the threads on the bolt or hole. This would quickly lead to a loose bolt, ovalling/wallowing out the hole, and the coilover separating from the LCA. Thankfully the LC was held up by the frame mounted bump-stop (clearly seen in your screengrab).

A 4runner without frame bump-stops will have no such luck…it will be a complete unrestricted collapse, with the tire coming up and smashing into the body, and the loose coilover assembly tearing up the tire, wheel, and CV. Depending on how far inward/upward the the tire/spindle moves, the CV and steering linkage could take out the differential and steering rack. The coilover getting wrenched around could even damage the top mounting bucket on the frame. This is nuts! Lets not think about the fact you would lose control of the vehicle instantaneously.

At the very least, toyota should design some sort of bolt retention system or safety wire the bolt so that the coil-over/bumpstop assembly can’t physically fall off. Properly torquing the bolt to spec may not be enough, if it’s being subjected to cyclic bending that could stretch the threads. At that point, a proper torque spec is irrelevant.

The 5th gen lower bolt mount design is so simple and robust…true double shear bolt mounted in a cradle at the center (front to back) of the control arm. It’s not going anywhere, because it physically cant.

 

I think the wheel more likely to take out fender and bend the strut outwards, which is less catastrophic than the scenario you describe (To be clear, I am not defending any of this.)

To make things worse, even if it happens under warranty, Toyota would have an easy way to deny claims due to abuse (i.e., offroading is not covered) or accident (i.e., hitting a pothole) exception clauses. Hopefully NHTSA will get involved in this matter sooner rather than later, because it also safety issue.

 

All of those potential catastrophes are definitely worth saving money on a little bit of steel and a chunk of rubber.

 

But think of the manufacturing time saved!

 

Three points make a triangle: LCA front and rear mounts and the shock mount. If the shock mount is in between the LCA mounts (front to back), then you shouldn't have any torsion on the LCA, regardless of the type of connector on the shock mount.

 

They are already banking on SR5 owners not knowing how to change a flat themselves.

The chance of a catastrophic failure is probably low when the vehicle is only used onroad and normal offroading (short of a high speed G-out or the vehicle getting air, or if the wheel gets stuck/wedged), and that's likely what their marketing research team found being the vast majority of users using the 4Rs as highlanders or even Corollas. They probably heard people saying the 5th gen was "over built" one too many time and took it seriously to find cost cutting where they can.

 

One could hope that it wouldn’t be catastrophic, but it’s only going to be worse than the example in the video.



Even though it was caught by the bumpstop in the picture above, you can see that already the tire is nearly torn open, and the CV is toast.

Without the bump stop, the tire will continue upward. The coilover is pinned at this point, and will push harder into the CV, and front keeps collapsing until the tire hits on the wheel well, or the frame touches the ground. Assuming the tire isn’t already deflated. If the travel is bound by the frame on the ground, the lower shock eye will probably hit the ground first. If you’re on soft ground, the coil over will probably be wrapped back around the LCA, and the metal starts to tear at the top bucket on the frame. Best case scenario is that it happens on flat ground and the vehicle tripods on the other three wheels and it holds the corner from falling all the way down.

I doubt this would be limited to vehicles used off road, since reports from Tacoma folks is that it’s not that difficult to get to the “bump-zone” valving where the hydraulic forces spike. Eventually that spiking would start causing failures I would guess. Keep in mind, the LC didn’t have to deal with the hydraulic spike issue, because it has normal shocks without the sharp “bump-zone” valving.

I’ll say this however…I’d be leary of bigger tires on 4runners specifically until this is sorted. The additional tire weight is unsprung mass… the added momentum will go directly into that spigot/bolt structure without the benefit of suspension cushioning.

 

I dont see a hole inside that tube for a bolt to thread into, or bolt thru.
It looks like the bolt that holds the shock into that mount broke off?
There are no threads, there is no thru-hole thru the A-arm, so did the bolt shear at the A-arm?

 

If it’s the same arrangement as the rear shock mount on the 5th gen, then the spigot tube is threaded. Actually, the thread itself may start past the tube inside the actual LCA structure.

That’s why I think that if the spigot and bolt experiences any bending forces when the suspension cycles, there is potential for the bolt threads to be stretched as a result, which means the bolt will naturally loosen.

The ovalling that I think I see in the picture might have been caused in the last moments as the bolt slowly backed out together with the eye of coilover, which forced the bolt up and down as it slowly unthreaded out of the tube, as the suspension cycles.


Edited: for clarity, and to say I’m not an engineer, but my first memories are of me breaking things just to see how they broke. Didn’t matter what it was, but I’ve always been enthralled with material, mechanical, and design failures. I’m the type that likes to read NTSB reports with my breakfast cereal. I’m taking educated guesses at how this stuff might fail, out of an interest in engineering, not so much to rag on the 6th gen, Toyota bean counters, or other Toyota folks.

 

A bump rubber on the shock shaft is as simple as a bump rubber on the frame. But I'll leave it to you to worry about these simple things after you complained for two pages on TW about not having a mechanical parking brake.

You're looking too closely at a screengrab from a Youtube video lol. Just look at your rear shocks as an example. It's a blind hole in the spigot for the bolt to thread into.

The LC300 that people here jerk off to has the same mount scheme. It additionally has a poorly placed sway bar that'll be bent on the first rock it hits:

 

A whole generation of 4Runner owners have experience with this lol:

 

Lower ball joint failure?

 

Yep. Frame-mounted bumpstops (two per LCA!) don't help if the knuckle separates from the LCA lol.