80 steering issues, wont track straight

[roaminglost]

Long one. Sorry. But I'd rather front-load it than get twenty replies telling me to check my caster.

1990 HDJ81. 4" lift, Delta 5L radius arms with 2.5* bushings stacked on top, 37x12.50R17 Mickey Thompson Baja Legend EXP on -38 offset beadlocks.

Symptom, and I want to be precise because I think the wording matters. This is not the loose, floaty wander people usually describe. Mine feels sticky. Small steering inputs meet resistance, so when the tire drops into a rut or groove the road wins and pulls me over. Then I correct, and it doesn't ease back, it holds and then breaks loose all at once. So I'm sawing left and right the whole way down the freeway.

The wheel does not self-center. Turn it at low speed, let go, and it mostly stays where I put it.

Done already:
Steering box rebuilt by Redhead
Frame reinforcement plates at the box, no cracks
U-joint at the box is brand new
Knuckles completely rebuilt, trunnion preload set at 12 lbs, 1000+ miles ago
All bushings replaced
Panhard corrected, axle centered
All new suspension components
Dobinson adjustable stabilizer, backed all the way off, no change

Alignment printout, Aug 14:
Caster 4.0 LF / 4.2 RF
Front total toe 0.17
Steer ahead 0.00
Thrust angle 0.03
Rear total toe 0.30 (haven't chased this yet, open to opinions)

Tested and ruled out:

Tire pressure. Ran 35 all around, then 40 front / 35 rear, then 40 all around. Steering effort got slightly lighter at 40 front but the crown-follow and the sawing didn't change.
Stabilizer damping. All the way soft, no difference.

Where my head is at. I don't think anything is broken. I think the caster is generating a return force and friction somewhere in the chain is eating it before it reaches the wheel. Sticky on small inputs points at bind, not wear. Candidates I haven't isolated yet: trunnion preload set at the top of spec and maybe not settling?

Questions:

1. Anyone at 4" with correct caster who still had this, what turned out to be the source
2. If you run Delta 5L arms, did you stack correction bushings on top like I did, and did Delta have an opinion on what that does to the axle's fore/aft position and the panhard relationship
3. Anyone measured breakaway at the knuckle after 1000 miles on a fresh rebuild, does 12 lbs hold or drop
4. Raised steering arm or panhard drop bracket at this height, did either actually change how it drives
5. Anyone on hybrid tires (Baja Legend EXP, Ridge Grappler, KO3) think the tire is carrying real blame here

Printouts and measured numbers appreciated. Happy to post more photos of the setup if it helps.

 

[bhsdriller]

steering box adjuster tightened too tight?

 

[roaminglost]

steering box adjuster tightened too tight?

i just got it back from redhead and ran it. so im not sure

 

[Shoredreamer]

Rear panhard correction definitely helps reduce the constant side to side steering input, especially in turns. What’s the history? How long have you had the issue? and did it start after something was added or changed on the 80?

 

[roaminglost]

Rear panhard correction definitely helps reduce the constant side to side steering input, especially in turns. What’s the history? How long have you had the issue? and did it start after something was added or changed on the 80?

its been corrected seems fine. and have a heavy rear sway.

seems to got worse when switching to the lift and 37s/ wheels

 

[jonheld]

This sounds like something mechanical.
Have you put the front axle on jackstands and looked/felt for binding?

 

[roaminglost]

This sounds like something mechanical.
Have you put the front axle on jackstands and looked/felt for binding?

Yeah, we thought it could be the knuckle preload, and it was literally 0 lbs at first, then rebuilt the knuckles and got 12 lbs with no shims. but havent checked it since

 

[peacesells63]

Are the panhard bushings OEM? is your front panhard bar adjuster tight? they tend to work loose with a lot of flexing.

Are you running a front sway bar?

I had a similar thing when I went to 37's. Mine was all in the tires, 37x12.50x17 e rated maxxis razr mt's crown pretty bad on an 8.5" wheel, so I have to run a max of 25psi in the front to keep it from wandering. At 20psi my 80 drives like a camry, at 40psi it drives like a model T.

80's generally drive like crap with lifts 3" or taller. Rear panhard correction helps, but the body roll input from a steep front panhard and the length discrepancy between the panhard and drag link really show up on taller trucks. Taller tires amplify that feeling as well. Add tire crowning into it and they drive like crap even with all of the "right" parts.

I have high steer and a 9.5" longer than stock panhard setup with the geometry corrected as much as possible - panhard and drag link Geometry is far better than stock height with my 3" or so lift. My truck stays remarkably flat in sharp corners with no front sway bar due to the better geometry and roll axis being much closer to the center of gravity, but it still handles god awful above 45mph with too much air in the front tires. Same symptoms you describe.

 

[jonheld]

Yeah, we thought it could be the knuckle preload, and it was literally 0 lbs at first, then rebuilt the knuckles and got 12 lbs with no shims. but havent checked it since

12 lbs of preload is above spec. Max is 9.9.
Spec is 5.6 to 9.9.

 

[roaminglost]

12 lbs of preload is above spec. Max is 9.9.
Spec is 5.6 to 9.9.

Yeah. They’re some opinions saying higher preload for 37” tires. So we have that a try. So lowering that pull is on the list

 

[ikarus]

Do you/did you have one of the JDM boxes with the steering sensitivity solenoid?

When did the symptoms first start? After the steering box reinstall, knuckles, 37s or...?

 

[roaminglost]

Do you/did you have one of the JDM boxes with the steering sensitivity solenoid?

When did the symptoms first start? After the steering box reinstall, knuckles, 37s or...?

Hard to say when tbh.

But I do have the jdm box

 

[ikarus]

Hard to say when tbh.

But I do have the jdm box

Maybe add that solenoid to the list of things to check? I know I drove mine once with it unplugged and the steering was super heavy at slow speeds and didn't feel right. I didn't try anything faster than 30 mph though

 

[roaminglost]

Maybe add that solenoid to the list of things to check? I know I drove mine once with it unplugged and the steering was super heavy at slow speeds and didn't feel right. I didn't try anything faster than 30 mph though

its plugged in right now but when i first got my truck it was missing that spring in the middle of it but since then i replaced it so it's complete. i was thinking of unplugging i to test

 

[MissahPapaJ]

I’d chalk test tires and play with tire pressures that’s nearly free to do and see if you get better results and go from there. Sound like things are fairly fresh and tight I’d lean towards a bad box, even good rebuilds are subject to potential premature failure. How healthy is your PS pump?

 

[roaminglost]

I’d chalk test tires and play with tire pressures that’s nearly free to do and see if you get better results and go from there. Sound like things are fairly fresh and tight I’d lean towards a bad box, even good rebuilds are subject to potential premature failure. How healthy is your PS pump?

Box is definitely better than it was but I’ll have to call redhead see what they say . Ps is new. And I’ve done 35-42psi range no change.

 

[Broski]

I think the tire pressure is playing a big role here.
IMO 35-40 PSI is to high for a 37” tire
On the street I run 25 PSI with 39s
It well documented bigger tires need less pressure.

 

[roaminglost]

I think the tire pressure is playing a big role here.
IMO 35-40 PSI is to high for a 37” tire
On the street I run 25 PSI with 39s
It well documented bigger tires need less pressure.

ill try dropping it today see if it helps

 

[roaminglost]

Update. Pressure is ruled out across the whole range, I’ve run 25 through 42 with no change to the sawing or the crown-follow, so I’ll stop chasing that one.


Preload is the standout. Jon, thanks for the FSM numbers. 12 lbs against a 5.6 to 9.9 spec means we’re over max, and it was set with no shims, so there’s room to bring it down. That’s happening this week.


Also going to unplug the solenoid and drive it. For the record my truck was missing the spring in the middle of it when I bought it, and I’ve since replaced it so the unit is complete.


Will report back with numbers on both.

 

[roaminglost]

Another update

Stabilizer. Pulled it off entirely rather than backing it off. Steering got noticeably less tight, which I'll take, but zero change to the self-centering. It was masking one symptom, not causing the other.

Knuckles. Dropped the drag link at the pitman and swung the axle by hand. Free, smooth, no notchiness through the whole range.

Box. Started the truck with the link still off and turned it. Free, no resistance, nothing sticking.

So the entire steering chain is loose and free and the wheel still won't come back. Nothing is binding. Which means either the return force is too weak or something is actively steering the truck.

Then I noticed this. Go over a speed bump with a slight steering input and the wheel shakes and moves on its own. It won't hold straight through the bump.

One detail I should have included up front: my beadlocks are -38 offset against a stock number around +25. Roughly 2.5" of tire pushed outboard per side and a scrub radius well outside what Toyota designed for. Longer lever on every road input. Probably amplifying all of the above.

Also talked to a guy running race chassis who ran his own 80 at 3 degrees, called it awful, and is happy at 5-6. Says 4 is bearable but it's the floor. I've already spent my correction on Delta 5L arms plus 2.5* bushings, so getting to 6 means a cut and turn or rear drop bracket

Questions:

1. Anyone measured bump steer on a lifted 80, what's an acceptable number
2. Anyone running -38 or similar offset on 37s, did going back to a higher offset change how it tracks
3. Anyone at 4" with big negative offset who's actually happy on the freeway