Death Shake- Any ideas?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Cube Dweller

Cube Dweller

Moderator
Joined
May 22, 2004
Threads
116
Messages
1,170
Location
22 Acacia Avenue
Vehicle is my 91 4runner, SAS w/ an '85 axle. Trunion bearings are 1 year old Timkins, some drag/preload. Springs are new waggy 44044's. TRE's are 555's, couple months old. Shackle angle is ~ 30* back from perpendicular to level ground. Toe is ~ 1/4" toe in. Tires are 35" MTR's, 38psi. I'm guessing about 4* of positive caster. I do have a steering dampener on the drag link. High steer is installed. Ubolts were torqued to 90 ft lbs a couple days ago when I installed the springs.

For some reason when traveling 5-15 mph and hit a mild bump, the front end begins to violently shake, wheels oscilating back and forth. It's uncontrollable and I have to come to a complete stop to get it to stop. Otherwise it drives pretty well, better than it did with the soft Trail Gear springs. I'm pretty lost and very frustrated at this point. Any suggestions on what to check? It's a daily driver and I'm losing patience :mad:

Thanks.
 
i dont have any answer but i am very interested in the fix. my friend blaine just did an sas recently on his pickup and has the same problem between 20-30 mph.

any help is appreciated
 
Death wobble comes in at around 35-40mph typically.. if it's doing it at that low of a speed, I think you've got bigger problems.

re-check the torque on the u-bolts, shackles, and spring hangar bolts, first.
Then, measure the caster.
Try also taking the toe in to only about 1/8"

Did he rotate the tires when he did the spring swap? A bent wheel can cause wobble too.
 
I'll drop the tire pressure to see if that helps.

This isn't death wobble with the weird, almost floaty feeling around 25-35. Been there, done that :D

This is a violent shaking...it's really weird, almost like the right bump causes the front end to resonate.
 
That's what death wobble is.. a voilent side to side shaking of the front tires that makes you think you're gonna die. That's what I was posting to. Never had the floaty feeling you describe.

Death wobble:
http://www.emotoman.com/videos/dw.mpg
 
Last edited:
Tony-Are you sure the caster is OK? That seems to be a root cause in many instances. The other big cause I've seen is worn/sloppy spring bushings.

When I got my 40 back together, I was worried about this since I have no stabilizer. However, it's been fine (Knocking on fake wood).

Post up what you come up with.
 
Check your ubolts and bushings,shackles .Had the same problem ended up being a combination of all the above .
 
my friends death shake is extremely violent when it happens. never happens over 35 ever. no stabalizer
 
IMOP my first step it's check torque in all steering and suspension components front. Measure caster and balanced your tires ..

I have double steering damper, caster over 2ª but just have a little shaking decreasing( braking ) speed around 30 - 40 km/h .. I found problems balancind my MTR tires ..
 
I have had death wobble on a few different rigs. It usually turns out to be to mostly related to caster (too much or too little) and the trunion bearing preload is not set correctly.

Easy test -- Try to get a set of 2* and 4* shims and play with different caster angles. Try 0* 2*, 6* and 8* total caster (since you already have 4* built in).

Harder test -- Take the steering knuckles apart and remove some shims to increase the preload on the trunion bearings.

I once had a DW when I put my hard top back on. I ran all sumer with the top off and no DW. The extra weight of the hard top sagged the rear down a little bit and added more caster to the front axle which caused the DW.
 
Last edited:
I would make sure your caster is set right and also retorque all bolts on the front end. Also, make sure your tires are balanced ... that'll give ya some good shakes..especially with swampers.
 
**Update**

I didn't mention before that the waggy spring bushings have 3/4" holes and are larger diameter than the Trail Gear or Toyota. Ideally I would have kept the 3/4 sleeves and used 7/16 bolts to clamp the sleeve against the shackle and tighten everything up. But the spring hanger and shackles were already drilled for 18mm so that wasn't an option. So I drilled out the shackles and hanger to 3/4 and turned down some new shackle spacers to the correct OD so the bushings don't squish out around them. I bolted everything up nice and snug and went for a test drive to the intersection that always causes DW. And.....








It still did it. So the wee bit of slop wasn't the culprit.

I took it in to the alignment shop in town. The two guys that run it both built and wheel pretty hardcore Toyotas and are pretty helpful with what works specifically for our type of rigs. My specs were:

Left Caster= 4.2* Right Caster 3.8*
Left Toe = 0.11 Right Toe = 0.49 :eek:

So after adjusting the caster stayed the same obviously, and they reset the toe to 0.02" on the left and 0.01" on the right. They like 0 toe in, though I know most peeps think ~1/8 toe in is good on SFA trucks with big tires.

Factory specs for an '85 runner are 2-4* of caster and 0.00 to 0.04" of toe per side.

So the results were:









Seems to have worked! I've driven it a few times over my favorite death wobble inducing sections of roads and while the steering wheel shimmys a bit, it doesn't end with death wobble implosion. I've driven it on the freeway a few times up to 70 and it feels pretty stable.

Regarding tires- I'm running 35" MTR's that aren't chunked and were very stable before I swapped out springs. While I'm confident the tires weren't the root cause, it's possible with the excessive toe in the big sidewalls on 8" rims exacerbated the issue.

So far, so good. Thanks for the suggestions.
 
You will never get the same caster numbers in knuckles in the same axle .. even if you measure it in a factory brand new axle ..

I'm not sure which are the rasonable tolerances between both side in caster numbers ..
 
Tapage said:
You will never get the same caster numbers in knuckles in the same axle .. even if you measure it in a factory brand new axle ..

I'm not sure which are the rasonable tolerances between both side in caster numbers ..
Click to expand...

It doesn't pull to either side, so I'm fine with 0.4 degrees of difference.
 
Check out all the play in your steering system. Are the joints all new? Have you adjusted/tuned all the play out of the steering box(very important)? how many miles are on the box? I have found a sloppy steering system enables the shake to happen. I run 36" bias ply tsl tires and in the morning until the get the flat spots worked out the do it from time to time. On my truck when the shake begins I punch it to accelerate about 5mph faster and it goes away.

Kirk
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 1 (members: 0, guests: 1)

Share this page

Back
Top Bottom