Broken Rear Lower Control Arm - Implications of Driving

[denvermaxd]

UPDATE/EDIT: If you're reading this thinking it's about a broken Lower Control Arm, it's actually about a broken Upper Control Arm. I misread the suspension diagram, because I'm like that... /UPDATE


I broke my Rear Lower Control Arm (Toyota part #48720-35051) off-roading last week. Broke it on the same trail that broke my rear sway bar in June.

I have a replacement rear sway bar, but had not installed it mostly due to procrastination.

It looks like it's going to take a couple weeks to get an OEM replacement into my hands without paying my local dealer's rather excessive price (~$300).

I don't drive many miles during the week, but I'm wondering if I need to just leave the T4R parked until I get this replaced.

My questions for the knowledgable folks here.

1. What are the implications of driving on-road with no rear sway bar and a broken rear lower control arm (passenger side)? Both safety and potential for additional suspension damage?
2. Was the lack of a rear sway bar possibly a cause of the LCA failure?

Thanks in advance for your input.

 

[mtbtim]

You're not going to want to drive your rig with a broken lower control arm for the reasons you already mentioned. That would not be smart. Definitely wait until you can replace it.

As for what caused the control arm to break, the lack of the rear sway bar could have contributed to it, since you'll get more articulation from the rear axle without the sway bar.

I'm not familiar with Littleton, CO. Do they salt the roads due to ice there? If so, is your undercarriage being attacked by rust? Sway bars do break, but mostly what breaks is the end links on either end. Control arms break as well, but it's not terribly common. For those that do suffer breaks, I think corrosion a lot of times has something to do with it.

 

[Sparky 97Runner]

I would think that driving with a broken rear control arm would make the rear of the vehicle extremely unstable and your rear wheel would probably be making intermittent contact with the wheel well. I wouldn't do it. Did you break it on a rock or something? A lot of people run without rear sway bars and this probably didn't contribute to your broken control arm. There are plenty of stories of bent rear lower control arms but rarely broken.

 

[denvermaxd]

Not much corrosion...

Thanks Tim. I'll park it until I get both rear LCAs and the Sway bar replaced.

In general my 4Runner doesn't have terrible corrosion considering how old it is , and mileage. But where the sway bar broke it looked like there was rust inside the bar.

The LCA, however, looks like pretty solid metal at the break point.

 

[denvermaxd]

I would think that driving with a broken rear control arm would make the rear of the vehicle extremely unstable and your rear wheel would probably be making intermittent contact with the wheel well. I wouldn't do it. Did you break it on a rock or something? A lot of people run without rear sway bars and this probably didn't contribute to your broken control arm. There are plenty of stories of bent rear lower control arms but rarely broken.

I don't think I hit a rock... would have had to be a pretty tall and narrow rock to impact where it broke, and I think I would have been concerned about clearance generally if I'd seen such a rock approaching.

Seems like it was just metal fatigue/age?

 

[Sparky 97Runner]

Wow! Those are interesting pictures. That looks like your upper rear control arm that's broken in the picture. PN#48720-35051 is for lower. And your right, not much corrosion. That's pretty crazy the upper control arm would break without corrosion or some form of trail contact.

 

[Sparky 97Runner]

Seems like it was just metal fatigue/age?

Yeah possibly. Or could be a bad weld from the factory. I don't think I've ever heard of a broken upper control arm.

 

[denvermaxd]

Some of the posts I see on this forum I have a hard time taking seriously so, that being said, a bit of a sarcastic comment is warranted here.

Sure, go ahead and drive it. You'll be fine.

But in all seriousness, nothing good can happen if you drive it like that.

Fair enough.

The more I thought about it, the more I began to think driving was a Very Bad Idea, but wanted confirmation.

For the record, I didn't realize I'd broken it until last night. Worth capturing the experience in case anyone else goes through the same:

Last Wednesday, while climbing Mosquito Pass from the Alma side, about halfway up I heard a metallic "bang" like a rock hitting my sliders or something, but right away my Spidey Sense was triggered. A short while later another metallic BANG, and I started focusing in on that and when it happened again about 20 yards along I started getting that creeping dread feeling.

The weird thing was, I was sure it was coming from the right front side, and it really felt/sounded like a "binding" and then release, like the 4wd was experiencing some internal tension and then popping. Not good, for sure. I was in 4L and shifted to 4H and for a while nothing, then it happened again. I pulled off and crawled all around under the right front looking for any obvious damage but found nothing. This reinforced my belief it was internal/transmission/drivetrain.

Turned around and drove down and it made the tension-release BANG like 5 times on the way down.

At this point, I was convinced it was my transmission or 4wd.

At the bottom I put it in 2wd and did not experience the sound again for a while, further convincing me it was my transmission. Was already planning an appointment at my local 4wd shop. Then pulling into the grocery heard the BANG again. My passengers were convinced it was right rear and not front at that point.

Got under the truck and couldn't see anything, which was either because:

- It was dark.
- The LCA had popped back into alignment at that point
- I just missed it.

Now I'm thinking it's something in the rear differential. But the noises basically stopped at that point. In hindsight, that's because I was now on paved roads and there was ostensibly zero articulation.

Drove 80 miles home. No noises, no instability (that I noticed).

:withstupid:

Pulled into my driveway and heard the BANG again. Now I'm finally thinking it must be the suspension. Maybe the rear spring? That's when I got under it again and noticed the LCA sheared.

 

[denvermaxd]

Wow! Those are interesting pictures. That looks like your upper rear control arm that's broken in the picture. PN#48720-35051 is for lower. And your right, not much corrosion. That's pretty crazy the upper control arm would break without corrosion or some form of trail contact.

OMG. I'm an idiot. You're right. It is the Upper Rear Control Arm. I just referenced a diagram and totally mis-identified which part was which.

:embarassed: :sorry:

Who would have thought the Upper was higher than the Lower? :redface:

woof. I think I'll go hide for a little while.

 

[Sparky 97Runner]

That's when I got under it again and noticed the LCA sheared.

Just wanted to make sure you understand that is your rear upper rear control arm broken in the picture and you said you ordered a new rear lower control arm in your first post. The earlier responses were assuming you had a broken rear lower control arm.

 

[Sparky 97Runner]

OMG. I'm an idiot. You're right. It is the Upper Rear Control Arm. I just referenced a diagram and totally mis-identified which part was which.

:embarassed: :sorry:

Who would have thought the Upper was higher than the Lower? :redface:

woof. I think I'll go hide for a little while.

LOL. No worries. Just wanted to make sure you get the correct parts for your rig. Meanwhile I did some google searching and apparently broken rear upper control arms are not that uncommon. Definitely going to be keeping a closer eye on mine from now on.

 

[denvermaxd]

Just wanted to make sure you understand that is your rear upper rear control arm broken in the picture and you said you ordered a new rear lower control arm in your first post. The earlier responses were assuming you had a broken rear lower control arm.

Yeah, I pretty much wasted everyone's time!! Sorry about that.

On the bright side, the UCA is cheaper.

I can imagine breaking the LCA would result in a lot of instability... and would be pretty hard to miss.

 

[brillo_76]

I have had 2 rear upper control snap while driving down the road in the past. The original upper control oem are solid rods with weld around bushing bracket.

The lower rear control arms our pipes with the bushing bracket welded on.

It's not a good idea to drive around with a snapped rear upper control arm like everyone suggest as the extra stress can snap the other side off as well.

I can't say for the off reading world as the conditions are different. Those who do that would know the best course of action to take.

I replaced my rear uppers with aftermarket pipe versions because I have lost 2 in 2 different rigs that are not off roaded at all. Both snapped right at end of the rod where the bushing bracket attaches. Both were not siezed either. Went up and down no problem.

So far I had good success going this route. However, it maybe alot better to run oem style upper rear control arms in the off road world.


From my observations, it's better to replace them with the pipe style versions. I can let you know on about 5 or 6 years if the upper rear pipe control arms are better. I only have a few years on them now.

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[brillo_76]

OMG. I'm an idiot. You're right. It is the Upper Rear Control Arm. I just referenced a diagram and totally mis-identified which part was which.



:embarassed: :sorry:



Who would have thought the Upper was higher than the Lower? :redface:



woof. I think I'll go hide for a little while.

Well all make mistakes. No biggie and no reason to hide...

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[shadow247]

I would think that driving with a broken rear control arm would make the rear of the vehicle extremely unstable and your rear wheel would probably be making intermittent contact with the wheel well. I wouldn't do it. Did you break it on a rock or something? A lot of people run without rear sway bars and this probably didn't contribute to your broken control arm. There are plenty of stories of bent rear lower control arms but rarely broken.

I can confirm. I have lost the front bolt, twice, for the rear LCA. How it didn't drop down and drag the ground is beyond me. The 1st time, was on a rough trail, and rear tire started rubbing like crazy over small bumps.

The 2nd time, I was going about 50mph... and when I hit the brakes, the whole truck changed lanes... I limped it a half mile down the road at 10mph and replaced the bolt on the side of the road in a church parking lot.

 

[Zhehan]

I can confirm. I have lost the front bolt, twice, for the rear LCA. How it didn't drop down and drag the ground is beyond me. The 1st time, was on a rough trail, and rear tire started rubbing like crazy over small bumps.

The 2nd time, I was going about 50mph... and when I hit the brakes, the whole truck changed lanes... I limped it a half mile down the road at 10mph and replaced the bolt on the side of the road in a church parking lot.

I've had blown bushing for the rear LCAs and that's bad enough. "Rear Steer" is an issue. I can't imagine losing a whole side! Geezus that must have been scary.

 

[brillo_76]

I can't imagine losing a lca bolt or control arm. It's bad enough when one of the uppers snaps. They immediately cause issues. The lower rear coming loose could be a flip over crash event. I'm glad all was well.


Did the bolts just snap, or did the nuts work themselves loose?

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[TheDurk]

I can't imagine losing a lca bolt or control arm. It's bad enough when one of the uppers snaps. They immediately cause issues. The lower rear coming loose could be a flip over crash event. I'm glad all was well.




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I had my left rear LCA bracket break loose while driving. Fortunately, I was on an empty interstate and had not gotten up to speed. It was really weird. The body shifted toward the side with the loose LCA, while the chassis kept proceeding normally in a straight line. If you think about it, the chassis doesn't know or care that the link is broken. The weird part was having to steer in a direction other that straight ahead from your reference point inside the body.

I pulled over and walked around the truck and soon figured out the cause. I was only five miles from home, so I was able to do an illegal U-Turn and get home going about 25 mph. It was fine going in a straight line, but turns were a little hairy. That led to the cosmic experience detailed in the thread linked in my sig, where you can see pics of the broken arm bracket.

 

[brillo_76]

You break off the frame or off the axle housing?


I know the lowers control arm brackets are notorious for coming off the frames.

Glad you got home safely

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[TheDurk]

You break off the frame or off the axle housing?


I know the lowers control arm brackets are notorious for coming off the frames.

Glad you got home safely

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The frame: