Cause of death wobble?

Ok chasing the death wobble, I've replaced all the rear control arms springs and shocks, only thing I didn't replace was the lateral rod. Went ahead and replaced the front struts. Worked for a week. Truck has an obvious list to the driver side rear corner. Fixing to rebuild the front end control arms, tie rod ends, ball joints. While researching this , concerning the front control arms and the rear lateral arm, Haynes states the bolts should be tightened with truck at normal ride height. Now here's my question the vin and door tag indicates this particular truck was shipped with 15" wheels, the previous owner replaced them with 16". This it seems would affect the normal ride height. Could this in anyway be the cause of the list and some of the wobble?

 

Did the PO or you also change the tire size? If the wheel size increased but tire ratio kept the vehicle at the same original height overall then no change to geometry. Once the wheel/tire size literally changes the height of the vehicle up or down then yes the suspension geometry would change. Did your replacement rear UCA and LCA directly replace or are they adjustable? If adjustable and you didnt specifically verify they're the exact same length then that could change the imaginary arc the rear axle follows as the suspension cycles up and down; similar discussion to be had if you do replace the rear track bar (aka panhard/lateral bar). But if they're all a hard bar (not adjustable) then disregard that thought.

Are the wheels all balanced correctly? Or yet another thought... 2001 runner, how are the wheel bearings? If you raise the rear and put the jack stands on the axle housing, try to shake the wheel itself. If there is any play outside of the regular fwd/back spinning, your bearing could be shot.

Looking at the front, is there anything up with the passenger strut/spring/sway bar end link somehow pushing up, making the rear sag like you see?

Try investigating some more and let us know your findings!

 

Need much more on this 'death wobble' deal as we have independent front suspension versus a solid axle up front.

Answering @iamincrediboy regarding your rear upper and lower arms would help considering that, if you replaced them with adjustable arms and didn't set them for factory length, you could have rear axle pull as the panhard bar attempts to center itself but tracks/pulls as suspension articulates. Also check your wheel bearings.

As for the front, only servicing needs are; replacement of your ball joints, control arm bushings, and tie rod inners/outers, and coilovers.

Your steering rack bushings could use replacing if they've never been replaced, but that would cause play in your steering and not the wobble you're describing.

Unbalanced wheels as mentioned above could also add to vibration; try rotating your wheels and seeing if the issue moves with the wheel?

 

Yeah, I've never heard of a death wobble for a 3rd gen.

I'd like if OP gave a very good description of what he's experiencing.

 

45 mph some what stable, as speed increases, even the minorest of bumps or imperfection in the road the whole truck sways sometime extremely. Rear control arm replacements were not adjustable, have not replaced panhard bar or bushings yet. It's hard to nail down because sometimes the body sway feels like it's a rear issue and sometimes the front. As far as the rear end bearings, the rear end was rebuilt last year. The whole thing is frustrating.

 

So, similarly, my rig, which I bought new in 2002, seems to sway a bit more than I'd like at 70mph+. They always swayed ("floated") from the factory at higher speeds a bit but I didn't think it was quite as bad as this past weekend. Up to 65 seems just fine.

I've replaced a good deal of the front and rear suspension. In the front, new struts, ball joints (upper and lower), upper strut mounts, end link bushings. In the back, same deal except for there not being any ball joints. All TOYOTA parts. I only did all that because of age.

What's left? I'm thinking it's now be the sway bar bushings? They looked fine. But they are original.

She's still got her original upper and lower control arm bushings. Could those play into things?

Springs are still original. My understanding is the shocks deal with the bumps and sway more than the springs do. Springs are ride height.

 

After doing a bit of google sleuthing, it appears that the rear lower control arm bushings are often the cause of swaying at higher speeds. Looks like I'll be replacing sway bar and front/rear LCA/UCA bushings soon. Can't hurt. Just wish I'd done it when I did everything else.

 

So doing some more looking...

The upper rear control arms have a good solid rubber bushing design that I really don't think is likely to go bad. https://partsouq.com/tesseract/assets/partsimages/Toyota/4871035040.jpg

Same with the panhard bar bushings.

The design of the lower control arm bushings is not solid and definitely looks like a wear item. https://partsouq.com/tesseract/assets/partsimages/Toyota/4872035051.jpg

I think I will replace just the lower control arm bushings in the rear of the car and see how she goes. The job looks really easy and I can go back and do more later without feeling like I wasted much effort.

Edit: Toyota also only seems to sell the rear LCA bushings so I'm thinking they know they don't last forever. If you want to replace the rear UCA bushings you can get the entire arm from TOYOTA or need to go aftermarket. For the front LCA/UCAs Toyota sells all the bushings.

 

I read in a thread somewhere, concerning rear springs. Someone posted that driverside and passenger side springs were different, I suppose to compensate for the fuel tank. I ordered a set designated right and left , the parts numbers and springs were identical, like I mentioned in the begining I have an at least 2" sag in the left rear. Some suggested springs from another model .

 

A large sag in one corner screams of a failed suspension component. Could be a wrong rear spring but that would be weird, could happen I suppose. Usually it's a broken spring or a mount is broken.

 

So. I pulled my rear lower control arms one by one and replaced the bushings with OEM ones from TOYOTA.

Felt no real difference around town up to 55mph. Got on the highway and it's a huge difference from 60-95mph. Before she would weeble-wobble a bit and I'd just use a light touch on her through bumps. Now that sway really seems to be gone. She felt so good driving on the highway. I don't remember her driving like this new but she must have. I just got used to her bad habits at high speed over the last 20 years.

Some tips:

Do NOT jack up the rig on jack stands. Leave the wheels on and the rig on the ground.

Jack up the OPPOSITE rear corner of the vehicle frame from the side you are working. Lift the body high but do not bring the wheel off the ground. This literally removes all tension from the control arm you want to remove. No need to fight it. No need for a pry bar. No need for a ratchet strap.

Unbolt the lower rear control arm you want to work on.

The OEM ones need to be pressed off and on. It will laugh at your 6 ton press. Go to Harbor Freight and get their $199 20Ton shop press. Now you do the laughing. I had a 32mm impact socket that worked to press them out.

Look at the bushings. If you are replacing them with OEM, notice how the nubbins in the rubber are LINED UP with the arm. You need to do the same before pressing in. If you go to a shop with your arms and bushings, make sure they know this.

If using aftermarket, there is nothing to line up and they don't need to be pressed in.

OEM ones were about $32 each from an online discount Toyota dealer. $52 each if you get them locally at retail. So ~$130 vs ~$210.

If you just don't care how much you want to spend, you can buy the whole arm for like $165 each, I think. I priced it but forgot. Then the job is ridiculously easy.

Looks like I do need end links on the rear sway bar as they look beat but still ok for now.

Sorry that this is probably no help to OP since he said he replaced his rear lower control arms already. Hope it can help someone else.

 

Cured mine with panhard bars also found out that my steering shaft was loose at the slip joint on the column at the base of the firewall was able to put 2 small spot wields on it until I got it replaced

 

I had similar characteristics on my 2001 when the LCA bracket finally rusted through. I'm sure you guys aren't dealing with that much rust, but just thought I'd drop this here.

 

Chasing the front end vibration on my 2002 4Runner I replaced the steering rack, all the bushings, struts. The vib lessened but was still there until I got a Road Force balance on all 4 wheels.