SCARY rear end float question

j.james

j.james

New member
:eek:

I have a question about the rear suspension of my 98 4Runner.

I'm on stock coils with recently replaced (~5kmi) stock black Tokicos, 1" body lift, and 265/75R16s with good tread.

There's a certain bump on the highway in the middle of a lazy 30° leftward corner that makes my rear end kick out about a foot to the right every time I go over it. It's incredibly frightening to have the rear end kick out like that at 65mph.

I usually just slow down and get off the gas while rolling over it and punch it coming out to straighten back out. Today, it had just rained, and after hitting the bump, my rear end floated about three feet leftward, causing me to go into the left lane nearly sideways (thankfully no one was in it) and almost roll my freaking truck. Scared me half to death.

Any ideas on why the rear end does this? Are my shocks not letting the coils rebound fast enough? Or is it too stiff? I don't know exactly the problem, but it's scaring me every time.
 
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Sounds like your rear springs are sagging. They are sagging so much that they are bottoming out on the nubbers. Replace the springs and the problem should go away.
 
I have the same issue when I drive over the one bump on a curvy road on a way to work. I have new rear springs and all new shocks. No rear sag at all.
I am guessing it is just a nature of the rear solid axle on our trucks?
 
That can't be normal. Is this the only car you have that has this problem? I have problems with tires on my 4runner, some slide a lot easier. But in general if this is happening you need to slow way down.
 
Tomsriv said:
That can't be normal. Is this the only car you have that has this problem? I have problems with tires on my 4runner, some slide a lot easier. But in general if this is happening you need to slow way down.
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The car is glued to the road when I drive the same "crazy" bump over sitting in my 2005 Legacy GT. :moping:
 
There is almost no wieght over the rear wheels, a high center of gravity and bad rear suspension cant react well enough at speed, plus you are getting air on the corner and bump, what do you think was gonna happen when you vehicle gets air while going around a corner, the back end will kick out because thats where the momentum is pushing it to go.
 
John, where in CT do you live? You may know the bump lol it's eastbound Rt. 84 in Waterbury right before Brass Mill Commons.

The rear end kickout only happens in my 4Runner. It's an ugly bump in other vehicles, but not the same: my Jeep with stiffer suspension takes it just fine, my cargo van with horribly sloppy suspension takes it just fine, needless to say my wife's Nissan Sentra glides right over it.

It's not just this one bump also, it's any bumps during leftward bends in the road that the 4Runner slides out.

And I understand the slowing down thing haha I do slow down considerably for this bump every time, this time the problem was just exacerbated by the wet road. I'm fully aware that slowing down will eliminate the problem, I just hate being the only goober going 45 on the major highway, so if it's something with the truck I can fix, I'll do it.

While I don't have any ostensible rear sag on my 98, the thought that it may be hitting the bump stops and bouncing up is interesting. I may have to go outside when it stops raining and see if jumping in the cargo area makes it contact the stops.
 
JohnsD90 said:
There is almost no wieght over the rear wheels, a high center of gravity and bad rear suspension cant react well enough at speed, plus you are getting air on the corner and bump, what do you think was gonna happen when you vehicle gets air while going around a corner, the back end will kick out because thats where the momentum is pushing it to go.
Click to expand...

Oh, this is just begging for a free body diagram!
 
Try lowering the psi in your tires. I know when the tires on my pickup are pumped up too much the rear will bounce out on bumps when going around a curve. So unless you are already running a low psi I'd try lowering it 5lbs and see if it helps.
 
kball said:
Try lowering the psi in your tires. I know when the tires on my pickup are pumped up too much the rear will bounce out on bumps when going around a curve. So unless you are already running a low psi I'd try lowering it 5lbs and see if it helps.
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Don't lower your tire pressure unless it is already too high or at the very high end of the operating range. Tires are meant to be at proper pressure and shouldn't be used as a crutch to cover a different problem. Just look at the Firestone disaster.

Just make sure you are in the proper range.
 
Nelsonmd said:
Don't lower your tire pressure unless it is already too high or at the very high end of the operating range. Tires are meant to be at proper pressure and shouldn't be used as a crutch to cover a different problem. Just look at the Firestone disaster.

Just make sure you are in the proper range.
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I agree, sorry if I wasn't too clear. I'm thinking his pressure is already too high like I said my truck tires were.
 
If it does a kinda chatter across the bump, it's probably too high of tire pressure. They should be run at ~35psi and not the high 50-80 that the sidewall says. The sidewall, on a LT tire, will show max pressure for max carrying capacity.

It the rear just feels loose, take a long hard look at the rear panhard bar. You may have lost a bolt or broken the bar. The PHB keeps the rear axle centered.

If the rear feels like it dips then shoots up, uncontrolled, it is probably bad rear shocks.

You can also get over-steer from a broken/disconnected FRONT swaybar. Check for broken parts there.
 
Just for clarification, it's a skittering motion, like I'm going too fast on a washboard corner, except it's only one bump and i just kind of flutter my tail end out to the right. I'm going to go check on the panhard bar and the sway links front and rear and will report back later.

Thanks for all of the suggestions, btw!
 
j.james said:
John, where in CT do you live? You may know the bump lol it's eastbound Rt. 84 in Waterbury right before Brass Mill Commons.

The rear end kickout only happens in my 4Runner. It's an ugly bump in other vehicles, but not the same: my Jeep with stiffer suspension takes it just fine, my cargo van with horribly sloppy suspension takes it just fine, needless to say my wife's Nissan Sentra glides right over it.

It's not just this one bump also, it's any bumps during leftward bends in the road that the 4Runner slides out.

And I understand the slowing down thing haha I do slow down considerably for this bump every time, this time the problem was just exacerbated by the wet road. I'm fully aware that slowing down will eliminate the problem, I just hate being the only goober going 45 on the major highway, so if it's something with the truck I can fix, I'll do it.

While I don't have any ostensible rear sag on my 98, the thought that it may be hitting the bump stops and bouncing up is interesting. I may have to go outside when it stops raining and see if jumping in the cargo area makes it contact the stops.
Click to expand...

I am trying to replay that part of 84 in my mind lol, maybe we can meet up and we can hit it in both trucks and see how it goes, im down in ridgefield, hit me up though, i have no problem traveling. I can meet up at nights or this weekend ill be back at school in NY this friday.
 
Ok i do know the bump, dont ever remember driving that part of the road in te 4runner, i usually only go to waterbury to see my tdi friend so i take the jetta, but im going to lake compounce tommorrow so if i have the 4runner ill see how it takes it!
 
so just an update, four months later :fishing: been busy haha

i called the local dealer and found out that my 4runner had never had the recalled rear coils swapped out, so i took it in and got the coils done and it solved everything. apparently i had been loading the rear up too much with gear and what-not and it essentially blew out the coils.

all's well now :D and now i'm gonna start a build thread.
 
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