Suspension Gurus, I need help. (1 Viewer)

[madisonr34]

Hello, my fellow mudders, I have a suspension problem and would like to get some insight from the suspension gurus.

My 97 FZJ80 rocks back and forth dangerously when my suspension loads and unloads at freeway speeds. For example, exiting a wide turn on freeway or a sudden lane change. This only happens at above 50 mph and if I am carrying a good amount of weight....let's say like 4 adults + 100lbs of stuff.

Specs: 1997 LX450
Stock factory springs. No sag. No lift of any kind
Good, 4 year old Nitto Terra. 285/75/16 Balanced 32 PSI cold
4 wheel alignment good
Bilstein 4600s
Factory sway bars with energy suspension bushings
ALL control arm bushings checked good
No body armor.

She drives perfectly at city speeds, no hiccups. The problem only occurs when I am carrying weight and at freeway speeds. I am thinking the shocks are blown but they work perfectly at slow speeds. Springs do not sag and I dont off road her. All bushings check out good. Maybe springs are shot??? Or do I need to upgrade something to carry that weight??

I am going to switch the suspensions to the stiffer KYB MONOMAX shocks and add Dobinson's variable stock height springs. Thoughts??

Thank you.

 

[baldilocks]

Swap the springs and shocks then report back.

 

[jpoole]

My guess is that you have weak shocks allowing the sway and some looseness somewhere that is amplifying the pucker factor of that sway.

If it handles well completely unloaded and worsens with weight that would have me looking at shocks as the primary source of this behavior. The shocks may just be under damped and getting overwhelmed by the increased weight when the 80 is loaded. Is it rocking/swaying side to side or is it more pitching fore and aft?

If you don't have sag and are happy with the ride height and ride quality most of the time I'd personally not be looking to change the springs. Soft springs aren't going to cause this type of issue but would primarily be a problem if ride height is too low, weight handling insufficient or similar, in my experience.

For any close to stock height and weight 80 that is driven "normally" I recommend a set of the OEM Tokico shocks which are priced well and designed to match the stock 80 suspension. I'm still running stock springs, with a touch of spacer to restore ride height, and Tokico shocks on my 80 and it handles and rides great in my opinion even with 280kish miles on the springs. I'm unloaded/light most of the time and like the spring rate and don't think that a stiffer spring would be an improvement for my uses.

There are a variety of components that can make handling suffer if they are worn or have slack. Loose wheel bearings, loose steering system parts, worn swaybar bushings and loose control arm bushings all come to mind. Many 80s also suffer from cracks on the frame around the steering box and similar front-end locations that are loaded by steering forces (even non wheeled stock 80s). Any of these can make it hard to keep the 80 on track which will make induced sway much harder to control and much more dangerous.

It's pretty easy to address all of the looseness/wear issues, including welding up frame cracks, and there's a lot of info on the forum about how to pull these repairs off. You can lay under the front of the 80 as someone moves the steering wheel back and forth to find some steering slack/play issues. You can usually visually spot cracks in the frame around the steering box, etc. and pictures on the forum will help you know what to look for. Lifting and pushing/pulling on wheels can help you find slack in wheel bearings/etc. Bushings can be harder to check in my opinion but a pry bar check and visual inspection can help if you know what you are looking for. If they are older or if you can feel slack as you transition from left to right turning, etc. it can make sense to just replace bushings to tighten up the axle tracking and sway bars.

 

[gummycarbs]

I am going to switch the suspensions to the stiffer KYB MONOMAX shocks and add Dobinson's variable stock height springs. Thoughts??

Replace them with "factory" Toyota, assuming you're happy with stock height. They're cheap and last a long time.

 

[1973Guppie]

KYB's are a great economical choice. Get a set of one inch lift springs in there. It will help firm things up. Make sure you replaced all the swaybar bushings with OEM and don't forget the frame to swaybar joints in the front. Good luck!

 

[BILT4ME]

Hello, my fellow mudders, I have a suspension problem and would like to get some insight from the suspension gurus.

My 97 FZJ80 rocks back and forth dangerously when my suspension loads and unloads at freeway speeds. For example, exiting a wide turn on freeway or a sudden lane change. This only happens at above 50 mph and if I am carrying a good amount of weight....let's say like 4 adults + 100lbs of stuff.

Specs: 1997 LX450
Stock factory springs. No sag. No lift of any kind
Good, 4 year old Nitto Terra. 285/75/16 Balanced 32 PSI cold
4 wheel alignment good
Bilstein 4600s
Factory sway bars with energy suspension bushings
ALL control arm bushings checked good
No body armor.

She drives perfectly at city speeds, no hiccups. The problem only occurs when I am carrying weight and at freeway speeds. I am thinking the shocks are blown but they work perfectly at slow speeds. Springs do not sag and I dont off road her. All bushings check out good. Maybe springs are shot??? Or do I need to upgrade something to carry that weight??

I am going to switch the suspensions to the stiffer KYB MONOMAX shocks and add Dobinson's variable stock height springs. Thoughts??

Thank you.

1) Check tire pressures to make sure they are correct across each axle.. 32 PSI seems a bit low for carrying 4 adults. Try 35 PSI. Each axle must be the same in both tires. You can run a few PSI higher in the rear when carrying a load.
2) Check the bushings on the front and rear panhard bars. These can cause serious handling issues for left and right oscillation
3) Make sure the sway bar bushings are tight and are installed properly on both front and rear sway bars. Don't forget to check the link rubbers as well.
4) Check for cracks in the frame around the steering gear.
5) Have your alignment checked for toe-in and advise caster. I know you're on stock springs, but with adding 4 people nd if your caster is marginal, it will push the alignment into an uncomfortable zone and can cause it to feel like it's darting around when loaded.
6) Check your nuts. The ones on the bottom of the steering arm at the bottom of each knuckle. If these are loose, it can cause play in the steering and it will not correct the steering until you have over-steered, then it will come back, giving the feel like swaying.
7) Consider an AirLift system with airbags in the rear axle to help control the ride height when loaded. You can add air when you have people getting in, then dump air when they get out. That system is about $1000. or you can get a manual air bag system for thee rear for about $100.

 

[Pascoscout]

32 psi cold is too low for significant weight. I'd bump up your air pressure to 40 or 45 psi and try again before dropping a ton of time and money on stuff. If I run 35 psi on mine, with the weight I have, the extra sway is noticeable. Bump up to 40 and it's gone.

If that does not help, when you say rocks back and forth do you mean the body of the car tilts from left to right or does it more feel like the body is sliding back and forth but staying relatively level? The first condition points to worn shocks, worn springs, low tire pressure or worn/lose sway bar components. The second condition could be worn or lose control arms, pan hard rods, lug nuts or wheel bearings. Issues with the steering box or steering arms would show up as being able to move the wheel a decent amount before feeling steering response on the ground. It often results in oversteer/over correction that can cause rocking.

 

[White Stripe]

Sounds like sway bar bushings. No pictures are provided so can't really say.