i just finished my 5inch sas on my 1990 4runner and i took it for a drive and on perfectly flat ground an i5 to 20 mph it drives OK but when i hit any bumps or dips the front tires start shaking violently from left to right until i slow back down. i only did the front so the back is 3in lower than the front... could it be not enough weight on the front cuz the back is lower? i aligned it 1/4 in toe in the best i could with a tape measure.also i have not installed the steering stabilizer yet. I'm stumped..... all help will be super appreciated... thanks

 

you need that steering stabilizer...sounds like that's the issue, reverberating the bumps thru the steering.

 

add the steering stabilizer, tighten up everything up front (springs and shackles especially), and make sure the preload on your knuckle bearings is right. mine had the same problem, and tightening everything up seemed to do the trick for me. i redid my knuckle bearing preload too... but it wasn't as effective.

 

It's called deathwobble - search.

The biggest factor is your caster, which is affected by the severe reverse rake you got going on. If you're gonna drive it at all, get a REALLY GOOD alignment ASAP, otherwise get one ASAP after you get the back at the right height.

A steering stabilizer will help, but it's more a bandaid on the problem, not a true fix.

 

tires that aren't balanced don't help either. I wouldn't worry about the deathwobble too much until you get the the truck finished up IMO.

 

Yup, death wobble it is and, as mentioned, a steering stablizer or lack of has nothing to do with it.
If the front end is correct you don't even need a steering stabilizer.

As mentioned, FIRST, get it aligned.
Caster MUST BE DEAD ON...
Make sure everything is tight.
Post up a picture, taken from the front, of the drag link/tie rod angles.







Fred

 

part of the problem it that the back end is lower than the front (adds a couple degrees of caster)
get the rear lift on it then get it aligned - problem fixed
live with it till then

 

TC has the best answer out of all. Your caster is way out and a stablizer is not going to solve your problem. being lower in the rear won't have that effect either. Some prerunners run like that on purpose with no problems. I'm running 40"tires with 14" coilovers in the front, no stabilizers and no sway bars and cruise down the freeway at 70+ MPH all day long.


My caster is et at -6 degrees and yours should be around that also. Get that right and make sure you have everything tightened up in the front and you should not have any more death wobble problems.