Chaplain

This question is regarding suspension systems on 4Runners. If it doesn't belong here please kindly let me know. I also did a search and did not find an answer to my question, so here it goes.

Why does the stock 4Runner rear suspension have a panhard bar and what would be the effect if it is removed?

What I think I know is on a parallel 4 link a panhard bar must be used. Its the bar that runs horizontally across the vehicle connecting the axle to the frame. Its required to limit the axle travel to only up and down movement, however it will induce a slight amount of side to side movement during suspension travel.

On a triangulated 4 link, simular to what the 4Runner has, the upper links keep the axle from rotating, keeping the pinion angle as constant as possible and the bottom 2 links keep the axle in place front to back. So this is where I'm confused, why the need for a panhard bar?

Thanks for constructive options and knowledge.

Thanks,
Steve

SacRunner

I believe it keeps the axle centered side to side. Look through the Offroad tech section, I believe there are numerous threads there at discuss the panhard bar and the need for a panhard drop bracket when the rear of a 4Runner is lifted.

I wish i could be more help to you, but I don't know all the functionalities of all the components of linked suspensions.

FredTJ

The 4Runners don't have triangulate upper control arms.
That's the need for the panhard, also called a trackbar.
The panhard (trackbar) registers the axle side to side.
The upper AND lower control arms are required to keep the axle from rotating and registering it front to rear.
Without the lower control arms (or the upper control arms) the axle would rotate a lot (causing massive pinion angle changes).


Here are some photos of the rear triangulated upper control arms:










You'll note that the uppers have to come together strongly above the rear diff in order to register the axle side to side and thus take the place of the panhard or trackbar.
With triangulate uppers the uppers perform three jobs (so the mounts have to be really strong, especially the frame mounts).
- They keep the axle from rotating.
- They work with the lower arms to register the axle front to rear.
- They register the axle side to side.




Fred

first4runner

fred said it best. but to simplify it.

The trackbar needs to be there if you have a 3-link susp, ladders, leaf springs, or a parallel 4-link susp.

On a triangulated suspension like fred said the upper control arms limit horizontal movement and keep it centered.

And it does not just keep the axle movement up and down. It is designed so that you can still have articulation meaning it keeps the axle somewhat centered even when you are flexing.

and both upper and lower links work together to hold onto your pinion angle, it is not just the uppers. It is kinda a push-pull thing going on.

and the need for it is because if you took it off, and where wheeling or going around a corner or something strenuous you risk the drive shaft hitting the gas tank and I assume possibly damaging your tank or warping your driveshaft and causing some nasty shimmying.

Hope that didnt confuse you any more.

Chaplain

I had the runner on the lift this past week while I installed a Total Chaos LT for the front. I'm trying to sort out what to do for the rear to get some travel out of it. To me, I'm no expert obviously, it looks like a triangulated 4-link back there I guess I'm wrong.

On my old 72 bronco when I linked it we didn't run a panhard bar and that thing worked awesome. It was what I believe is called a triple triangulated setup? Bottom links went to the center and uppers went to the frame rail. (I didn't do the math/design for it, just did the work.)

I'm looking at a tri-link diagram that is suggesting no need for a panhard bar??

The real question is how do I get some travel out of this rear end? I was thinking of putting longer arms on it and ditching the panhard, but then theres that thing about the gas tank and the upper arms....

Chaplain

I had the runner on the lift this past week while I installed a Total Chaos LT for the front. I'm trying to sort out what to do for the rear to get some travel out of it. To me, I'm no expert obviously, it looks like a triangulated 4-link back there I guess I'm wrong.

On my old 72 bronco when I linked it we didn't run a panhard bar and that thing worked awesome. It was what I believe is called a triple triangulated setup? Bottom links went to the center and uppers went to the frame rail. (I didn't do the math/design for it, just did the work.)

I'm looking at a tri-link diagram that is suggesting no need for a panhard bar??

The real question is how do I get some travel out of this rear end? I was thinking of putting longer arms on it and ditching the panhard, but then theres that thing about the gas tank and the upper arms....

FredTJ

Well first you have to find out what's limiting your travel, correct ?
Most likely shocks and/or sway bar.




Fred

Chaplain

This is what I came up with: https://www.yotatech.com/forums/f88/...runner-132149/

tc

The rear is indeed triangulated on the uppers.

The question is are they triangulated ENOUGH to provide the lateral control of the axle...

FredTJ

Post up a photo.
Generally 40* angle on the arms will do the trick.



Fred

tc

I'll get a photo and/or some measurements tomorrow, but I doubt it's 40*

tc

22" across at the axle, 29" across at the frame, uppers are about 12"

So, the angle is about 17* between the link and the centerline of the vehicle, 34* between the links.

James Dean

There is not enough triangle on the uppers. Plus they are too small to handle all the side to side torque. Also the upper mounts were never designed for that kind of load.
Jack your runner up and unhook the panhard bar and see how much you can move it back and forth. Then imagine 4000lbs doing it, oh and throw in an angle on a hill. Squeeze a spring (ink pen type) in between your fingers at an angle and see how far you can go before it flies out.

FredTJ

You want 40* or so angle in the uppers before you can trash the track bar.
As already mentioned, you'll need to beef up the upper, frame end mounts, however that isn't a tough job.






Fred