Engine Compartment Body Flex Discussion Only

daToy · 08-14-2007, 09:27 PM

All,

I moved this and started a new thread to JUST discuss the flex issue. This discussion is getting lost in the other thread. We need to look at this and do some of our own work so we can define the root cause. We can then be sure that Toyota solves the real problem If they don't we will be able to look towards our own solution.

PLEASE KEEP DISCUSSION ON TARGET IN THIS THREAD!!!!!

I did some flex testing. You will have to excuse my garage tools. I hope this help shed a little light on the issue. I looked at the front body mount for compression and also setup a gauge mounted on one side of the body and used it to measure any deflection on the other side. Note that this test was done in a static environment. If you add dynamic forces the frame will most likely flex even more.

The test showed no flex in the body but 1/4" compression of the right bushing. this was with the FJ lifted 17" on the left front. I did not get the left rear tire off the ground which was my original intention but it was just to height to go with the high lift.

With additional lift of the left front to the point the where all weight is removed from the left rear may show additional bushing compression (there is not much left) and then start transferring the flex to the body.

The following picture show what I did.

Pre flex gauge

Pre flex left bushing

Pre test right bushing

First test at about 12"

Gauge

Left

Right

For the second test I loosened the bottom bushing on the right side to see if that would allow any more movement in the top. No additional space was noted.

Left

Right

For test 3 I took the right side up to 17"

Gauge

Left

Right

Jack Height

FJ From front

Left bottom bushing

Left right bushing

Summary:

This test shows torsion flex in the frame under static load. I did not even get maximum lift on the left hand side. With the rear tire totally unloaded and dynamic forces added there will be additional flex in the frame. The bushings will reach maximum compression and the forces will then be applied to the body.

daToy · 08-14-2007, 09:37 PM

There was some discussion that my test gauge was not valid. My assumption was that if the body was being distorted one side would push up and the gauge would show this.

Another way to do this would be to pick 4 reference points on the front of the body that represent the 4 corners of the front as a square. A measurement could then be taken diagonally from the lower point on one side to the upper point on the other. This would show any distortion of the front box.

Any distortion on the horizontal plane from the front of the fender to the back should show up by using a straight edge.

Comments?

FJR Colorado · 08-15-2007, 10:42 PM

Do yourself a favor...

Don't ever use a HiLift jack in that manner

therelaxer · 08-15-2007, 11:03 PM

Quote:

FJR Colorado previously said:

Do yourself a favor...

Don't ever use a HiLift jack in that manner

That HiLift you setup is scarier than the engine bay rips and tears.

Savvyav · 08-15-2007, 11:05 PM

Quote:

therelaxer previously said:

That HiLift you setup is scarier than the engine bay rips and tears.

Looks like he used the wheel hook atch..... suppose to work like that...yeah?

FJR Colorado · 08-15-2007, 11:09 PM

The problem is the 4" wide block he has it sitting on. It appears to be on the verge of kicking right out hence dropping the vehicle and sending the jack into his fender (or worse).

Wadi · 08-17-2007, 05:33 AM

Quote:

FJR Colorado previously said:

The problem is the 4" wide block he has it sitting on. It appears to be on the verge of kicking right out hence dropping the vehicle and sending the jack into his fender (or worse).

Agreed. Furthermore someone had to get underneath to take the measurements.

DaToy is right regarding the need to build an argument for a likely root cause. Unfortunately, this isn't the way to do it. Actually, applying a fixed unrealistic load like that is good way tweak the frame. The load is unrealistic because in true-off road conditions the suspension on the lifte corner would be fully compressed creating a different load on the body.

mach · 08-19-2007, 09:35 AM

Quote:

Wadi previously said:

Actually, applying a fixed unrealistic load like that is good way tweak the frame. The load is unrealistic because in true-off road conditions the suspension on the lifte corner would be fully compressed creating a different load on the body.

Tweak the frame? Unrealistic load? If you have ever taken your FJ offroad it's seen 10 times the force being applied here. Dynamic situations (like going over rocks, trees, jumps, or even speed bumps) cause huge spikes in forces that can cause this kind of damage. That's probably why the first to report the problems were those who were jumping their FJs. You can jump it once and bend it, or just drive it long enough and it'll eventually bend anyway. Or so it seems.

By the way, the suspension is fully compressed because he picked it up by the wheel. Regardless, that hi-lift does look like it's ready to pop out and kill someone. Be more careful.

daToy · 08-19-2007, 09:51 PM

No one was EVER under the FJ. I have long arms and only the front motor mounts were measured... I was very slow and careful with the jack and the tires were well blocked. The FJ was jacked to the full extent of the jack with the jack on the ground first to test and then the block was added. You also can't see the 10 ton jack stand that was under the FJ while the photos were being taken. (I have 4 and they are extensively used when ever I get close to going under the FJ.)

The static forces in this case are MUCH less that you will ever get in a dynamic situation. Drive the front left up on a rock and you will create this exact load on the frame.