Play in steering only when descending rough tracks (1 Viewer)

[bug616]

I’m not sure where to start with this and would appreciate some advice.

I am currently touring South Eastern Europe off-road. Done about 1200km so far with approx 2000km left to go. Tracks are predominantly loose gravel but often very rough with large stones.

My steering issue is only noticeable when descending steep rough tracks either using the brake or engine braking to hold speed around 5mph. As the front wheels are going over the bumps I feel noticeable play in the steering. When I stop and turn the wheel there is no play. There is also no play when driving other surfaces.

Be good to know where to start with this. Pretty sure it isn’t wheel bearings. I’ve no other symptoms and rebuilt axles just before the trip. Haven’t jacked it up yet but there doesn’t appear to be any play in the ball joints.

 

[bug616]

Checked knuckle studs and they’re all good

 

[mudgudgeon]

Has the suspension been lifted?

What was done to correct caster?
Do you know what caster numbers you have?

Why do you say not wheel bearings?
What method did you use to torque/preload bearings?

Have someone rock the steering wheel back and forth while you watch for movement in the steering and suspension.

 

[Rwhat]

I would check wheel bearing pre load.

 

[bug616]

Has the suspension been lifted?

What was done to correct caster?
Do you know what caster numbers you have?

Why do you say not wheel bearings?
What method did you use to torque/preload bearings?

Have someone rock the steering wheel back and forth while you watch for movement in the steering and suspension.

3” suspension lift corrected with 3” drop brackets. Don’t have castor numbers with me but when last checked were in spec.

I didn’t suspect wheel bearings as no other symptoms but will check and report back. Torque/preload set using the Tools method (I am on 37s) and secured with Trail Gear lock nut.

All bushes also seem good - all have been replaced with new OEM within last 15,000 miles.

I have checked for play in steering and cannot see or feel any but this is with wheels on the ground. I am looking for a garage where I can get it jacked up to check further.

 

[mudgudgeon]

Are you wheeling with tires aired down? What psi?

I notice a huge change in steering with tires aired down.
On 35s below 20psi, steering becomes vague and unresponsive because sidewalls flex.

 

[mudgudgeon]

I am looking for a garage where I can get it jacked up to check further.

A good redneck would ramp it up on a kerb in the shopping centre car park and crawl under it.
You want to test for play in the steering with the wheels on the ground so there's resistance at the wheels.

To check wheel bearings, jack tires of the ground.

 

[bug616]

Are you wheeling with tires aired down? What psi?

I notice a huge change in steering with tires aired down.
On 35s below 20psi, steering becomes vague and unresponsive because sidewalls flex.

Yeh, I’m not new to this. I’ve done 10,000s miles off-road touring in this truck on this setup. Never had this feeling in the steering before. The pressures I run are specific to the fact I’m on Michelin XZLs 255/100r16 and the truck weight of 3300kg - this type of rocky terrain is 30psi front, 32psi rear. Road pressures are 50/52psi respectively.

This is not a vagueness in the steering but when holding the steering wheel dead straight I get a knock through the steering wheel with a significance amount of slop, like a loose u joint. Only when moving over large stones that move under the wheels. Stop and it’s not there. Steering is tight on the road as it should be.

I’ve checked all steering links with wheels on the ground and there’s no visible play. I am leaning toward one of the steering column U joints but want to check wheel bearings first. My situation is complicated by my being in Montenegro, on a campsite that doesn’t allow working on vehicles, and my jack currently in use on my trailer! I’ll trying to sort a jack at the minute.

The truck

 

[BucketEighty]

Have you checked the panhard bar mounts? Could be ovalized hole(s) on the panhard bar brackets.

 

[bug616]

Have you checked the panhard bar mounts? Could be ovalized hole(s) on the panhard bar brackets.

Kind of wish it was this as would be easy to sort. Just checked and no go. Bolts torqued to spec. Bushes all good and no sign of ovalized holes.

 

[Broski]

Look at the panhard mount at the frame !
The tire psi numbers are very high how did you come up with those.

 

[mudgudgeon]

Check the frame for cracking around the steering box, and around the panhard rod mount and brace?

Cracked frame can be felt as a clunk, knock etc

Not familiar with this tire but agree, the pressure seems very high. Though, not sure it's gonna be a factor here

 

[ChaseTruck]

So this only happens when one of the front tires is in the air and doesn't bear any weight?

 

[Fosters]

Steering box slop…

 

[lumbee1]

@bug616 do you ever get the knock and slop on the road in any situation or does it only happen with suspension movement going over rocks?

 

[bug616]

@bug616 do you ever get the knock and slop on the road in any situation or does it only happen with suspension movement going over rocks?

Only going over rocks either engine braking or using brakes. Don’t feel it going over same rocks up hill under power

 

[bug616]

Steering box slop…

If it was this I’d expect to notice it on all surfaces and I don’t. Steering is tight on the road

 

[BILT4ME]

When you are descending and on loose rocks and gravel, the load on the wheels and driveline comes and goes as the rocks roll, slide, and stop the wheels.
All drive line slop (drive flanges, birfs, splines, spider gears, ring and pinion, slip yoke, u-joints, transfer case) all gets taken up and released over and over. Going downhill has different physics than climbing up the hill where all your power is in one direction. Downhill, it reverses taking all slack both directions then powering, then release because you are using brakes and engine braking.

I don't think you have anything "loose". I think it's experiencing a different dynamic.

Are you running the air conditioner during this time? Because that will idle up the engine and cause you to use brakes and acceleration, then deceleration frequently.

 

[bug616]

So this only happens when one of the front tires is in the air and doesn't bear any weight?

Not in the air as such as speed is 5mph max but when the loose rocks are causing the front wheels to lose traction

 

[bug616]

When you are descending and on loose rocks and gravel, the load on the wheels and driveline comes and goes as the rocks roll, slide, and stop the wheels.
All drive line slop (drive flanges, birfs, splines, spider gears, ring and pinion, slip yoke, u-joints, transfer case) all gets taken up and released over and over. Going downhill has different physics than climbing up the hill where all your power is in one direction. Downhill, it reverses taking all slack both directions then powering, then release because you are using brakes and engine braking.

I don't think you have anything "loose". I think it's experiencing a different dynamic.

Are you running the air conditioner during this time? Because that will idle up the engine and cause you to use brakes and acceleration, then deceleration frequently.

This is exactly it - you’ve described it much better than me.

The track that I noticed it on was a 600m vertical descent in around 1.2 miles, so it was pretty steep and very loose rocks. AC was on but I’m regeared to 4.88 and have low range reduction gears, so even 2nd gear kept my speed around 5mph without me needing to touch the brakes. Over the course of the descent I tried engine braking only in 1st and 2nd gear, and I tried being in neutral using the brakes. The issue was present in all situations.

I have been noticing some slop in the drivetrain over the past three days as I did a 180 mile off-road trail. I also noticed my birfs are sometimes clicking, again most noticeably when descending very tight switchbacks. Birfs and axles are original Bobby Longfields with approx 60k miles on them. They were recently swapped sides with new flanges but are perhaps nearing their end…. I suspect there is some slop in my prop slip joints as well.

I will get it jacked up tomorrow and ensure wheel bearings are good and no issues with panhard or chassis cracks.