Death wobble, KZJ78

[Lomoski]

Hi gang,

So I just put my 33x10x15 k KO2's back on my rig. I've had them balanced three times now and I still have a death wobble starting at 70km/h. If I hit a bump it starts shaking pretty violently through the steering wheel. I had them balanced at a reputed four wheel shop, then at a road force balance and then again at a toyota dealership with road force again. So I'm confident it isn't the balance.

Information about the truck.

Lifted with dobinsons springs and shocks with a new steering dampner. 3 inch lift
Tie rod ends and relay rod ends replaced
Wheel bearings replaced 1 year ago
Sway bars extended with lift
castor correction bushings installed
correct toe in



Where do I go next? It has always pulled slightly to the left but it didn't wobble so badly with my 31's but it did have a wobble. Would adjusting the steering box a little tighter on the adjustment screw help at all?

I can't see anything obvious like a bushing or anything like that. When I had the control arms off to press the castor correction bushings the rear bushings looked fine.

Steering pump leaks a little bit, plan on rebuilding but doubt that's the issue.


Any suggestions are welcomed. I have done some research and everyone seems to say castor, but I've already corrected that with rubber castor correction bushings from dobinsons.


Thanks guys

Marc

 

[Nas90tdi]

That's very odd with your list of maintenance, you hit the high spots that usually contribute to death wobble. I am running the exact same set up including the same tires. And, have no sway bars.
The castor angle can cause it, but isn't always the root cause.
One thing you should check is the alignment since you said it's pulling a little. You can do that yourself easily enough. If you have too much toe in it can cause a hopping of a tire essentially as it catches on the edge and fights against the other tire.
Some lifted Jeeps actually have to run a touch of toe-out to stop the death wobble.

Tightening the steering box would only mask it ,if it did anything at all. Highly unlikely it would be the cause.

 

[Lomoski]

That's very odd with your list of maintenance, you hit the high spots that usually contribute to death wobble. I am running the exact same set up including the same tires. And, have no sway bars.
The castor angle can cause it, but isn't always the root cause.
One thing you should check is the alignment since you said it's pulling a little. You can do that yourself easily enough. If you have too much toe in it can cause a hopping of a tire essentially as it catches on the edge and fights against the other tire.
Some lifted Jeeps actually have to run a touch of toe-out to stop the death wobble.

Tightening the steering box would only mask it ,if it did anything at all. Highly unlikely it would be the cause.

Thanks,
I have checked the toe in and it is within spec, maybe I should try a little extra toe out. Would king pins/knuckles cause a death wobble?

I'm going to check my wheel bearings again tomorrow, but I doubt that's the issue.

Thanks for your input

 

[CharlesHS]

I would not touch the steering box pinion load adjustment; that is one of those adjustments where a little goes a long way and it could wear out your steering box quicker if adjusted incorrectly.
Have you checked the spindle housing bearing load top and bottom ?
If these are out of adjustment or worn; they can cause what you are describing.

 

[Lomoski]

I would not touch the steering box pinion load adjustment; that is one of those adjustments where a little goes a long way and it could wear out your steering box quicker if adjusted incorrectly.
Have you checked the spindle housing bearing load top and bottom ?
If these are out of adjustment or worn; they can cause what you are describing.

I'm not sure if I know what you mean by spindle housing bearing load. Is that the king pin bearings?

 

[CharlesHS]

YES.... That is probably what they call them

 

[roscoFJ73]

Would king pins/knuckles cause a death wobble?

Anything and everything can cause a death wobble. The suspension shop I go to told me they make try to make the death wobble worse, then dial it back, but thats a bit easier on a leaf sprung front. I also wouldnt touch the steering box adjustment unless its out of spec

 

[Lomoski]

YES.... That is probably what they call them

Are they adjustable externally or do I need to disassemble the birf?

 

[CharlesHS]

There are shims that create the load on the bearings. You can adjust externally but you will need to partially disassemble to get a good feel for load. There are other members far more experienced that can assist you with maintenance and load adjustment.

 

[Loober]

I've had a situation where the eyes of the spring leafs would shimmy back and forth on the bushings causing weird steering vibrations. Check that out too

 

[Lomoski]

I've had a situation where the eyes of the spring leafs would shimmy back and forth on the bushings causing weird steering vibrations. Check that out too

I've got coils and control arms on mine, but I appreciate the input.

 

[Hugh Heifer]

The two things I have noted to cause death wobble more than anything are worn out spring bushings (which you don't have) and worn out trunion bearings in the top and bottom of the knuckles. Is the KZJ78 knuckle similar in set up to a solid axle knuckle? I have never messed with one.

 

[Lomoski]

The two things I have noted to cause death wobble more than anything are worn out spring bushings (which you don't have) and worn out trunion bearings in the top and bottom of the knuckles. Is the KZJ78 knuckle similar in set up to a solid axle knuckle? I have never messed with one.

It is indeed a solid front axle with knuckles. I think my panhard bushings are in need of replacing as well. Original with almost 300k on it. Looks like it might be time to order a knuckle rebuild kit as well. Have you rebuilt knuckles before? I'm quite mechanically inclined and have done all my own work on my cruiser so far including head replacement. Within my realm?

Cheers

 

[SNLC]

It is indeed a solid front axle with knuckles. I think my panhard bushings are in need of replacing as well. Original with almost 300k on it. Looks like it might be time to order a knuckle rebuild kit as well. Have you rebuilt knuckles before? I'm quite mechanically inclined and have done all my own work on my cruiser so far including head replacement. Within my realm?

Cheers

There ya go, Panhard is where I would look.

As long as the trunnion, that’s what Toyota calls king pins, and wheel bearings are good Panhard is next as well as caster specs. How much lift?

Is this a regular thing that always happens at 70kmph?

I have only experienced it once when I couldn’t track it down and it only happened once. But it was a violent death, very. Pulled over and couldn’t find anything. Happened in a hard heavy down hill turn at speed.

I finally decided it was welded on caster plates which you don’t have or it was tie rod contacting radius arm.

I agree don’t touch steering box unless you have done everything else.

Cheers

 

[Lomoski]

There ya go, Panhard is where I would look.

As long as the trunnion, that’s what Toyota calls king pins, and wheel bearings are good Panhard is next as well as caster specs. How much lift?

Is this a regular thing that always happens at 70kmph?

I have only experienced it once when I couldn’t track it down and it only happened once. But it was a violent death, very. Pulled over and couldn’t find anything. Happened in a hard heavy down hill turn at speed.

I finally decided it was welded on caster plates which you don’t have or it was tie rod contacting radius arm.

I agree don’t touch steering box unless you have done everything else.

Cheers

I would say it's pretty regular between 70 and 90. Pretty solid wobble. If I hit a bump it really starts jumping.
I have a 3 inch lift, I've had the tires balanced 3 times in a week, 1 non road force and 2 times roadforce. I have castor correction bushings. New tre and relay rod ends. Wheel bearings are 1 year old. As is the lift, shocks and steering damper

 

[MUDZLLA]

4-wheel alignment? Frame alignment check? Just throwin stuff out there...

Only death wobble I ever experienced in my 80 was trying out 37" bias ply Super Swampers. Went away when they did.

 

[SNLC]

If you hit a bump and get death wobble on a coil sprung truck, very good chance it is your Panhard.

What you are describing is called bump steer. Does it only do it between 70-90?

The panhard has to be on the same angle as the drag link on the steering or you get bump steer. Look at it from straight on, is the Panhard on the same angle or plane as the drag link? Lifting brings these things out of spec, basically when you lift be it coils or leaves it rolls the axle forward. This is why caster goes out of spec too. It is also why adjustable panhards are made because lifting also takes the axle out of center on a coil sprung truck.

Cheers

 

[kbushnz]

I got that and it turned out the panhard rod bush was loose.... was really scary... just came out of the blue. Once fixed it felt sooo much better. I also replaced the steering dampener after that too as the factory one was stuffed.

 

[lrd2sea]

If you hit a bump and get death wobble on a coil sprung truck, very good chance it is your Panhard.

What you are describing is called bump steer. Does it only do it between 70-90?

The panhard has to be on the same angle as the drag link on the steering or you get bump steer. Look at it from straight on, is the Panhard on the same angle or plane as the drag link? Lifting brings these things out of spec, basically when you lift be it coils or leaves it rolls the axle forward. This is why caster goes out of spec too. It is also why adjustable panhards are made because lifting also takes the axle out of center on a coil sprung truck.

Cheers

Sounds legit. But I have no idea of any elements you mentioned, snlc. Is it possible for you to post a foto, or a drawing?
Just had mine for 2 months, 2009 trolly 4.2 naturally aspired.lifted about 2-3", 285/75_16 tyres, rear with 2" spacers, as I can tell. Aligned, two front wheels balanced.b
wobble happened only at 85 kph, once past that it runs smoothly again. If I didn't pay attention and stay at 85, it worsens nd the death wobble developed.

 

[SNLC]

Here is a couple pics,

This is 2007+ 70-series.

This is a stock 92 Prado.

Just change the panhard bushings out. Go test and see if it is still doing it. If it is we will troubleshoot it some more.

Cheers