You hit a bump at 80 km/h, the front end starts shaking side to side, and the only thing that stops it is braking hard. That's death wobble, and a GQ or GU Patrol on big tyres and a lift is the most likely 4WD in Australia to do it. It is never one thing. It's two or three worn parts that each would be fine alone.
Why Patrols get it
A solid-axle Patrol front end is held in place by two radius arms, one panhard rod and the steering. Every one of those has rubber bushes. When the bushes get soft, the axle can shimmy, and the big tyre and heavy wheel turn that shimmy into an oscillation. Lift the Patrol and you make it worse: the radius arms now point downhill, caster drops, and the steering loses the self-centring that would normally damp the shake out.
The order we check, because order matters
1. Tyre balance and wheel bearings. Boring, but it's the trigger half the time. An out-of-balance 33 or 35 at 80 km/h is exactly the input that sets everything else off. Then wheel bearing play: jack it up, grab the tyre at 12 and 6 and rock it. Any movement is bearing or swivel hub.
2. Swivel hub preload. Patrol-specific and often missed. The swivel hubs on a GQ/GU have king-pin bearings that must be preloaded with shims. When they're loose the whole stub axle can wobble on the housing. Grab the tyre at 9 and 3 and rock it with the steering locked; play there that isn't the tie rod is swivel hubs. We rebuild and re-shim them.
3. Radius arm bushes. The number one cause on a lifted Patrol. The chassis-end bushes let the axle walk fore and aft. If the Patrol is lifted more than 2 inches and still on standard arms, you also need caster correction: either offset bushes or caster-corrected radius arms. We fit both, and we'll tell you which you need based on the lift height.
4. Panhard rod bushes and the panhard mount. The panhard stops the axle moving sideways. Worn bushes, or on a GU a cracked chassis-side panhard mount, let the axle shift left-right over bumps. Check the mount for cracks every time; we've welded plenty.
5. Steering damper. It hides problems rather than fixing them, but a dead damper lets a small shimmy grow. Replace it after the bushes, not instead of them.
6. Tie rod ends and drag link. Standard wear check. On a GQ the drag link ball joints are serviceable and usually loose.
7. Steering box free play. The last one, and the one most workshops never touch. See below.
Lifted Patrol: the caster fix
If your Patrol has a 2-inch or taller lift and wanders on the highway, needs constant correction and wobbles over bumps, the caster is wrong. On a GQ/GU, caster comes from the radius arms. Offset bushes recover about 2 to 3 degrees and suit a 2-inch lift. Above that you need adjustable or caster-corrected arms. Doing this transforms a lifted Patrol on the highway, and it's the fix most people are chasing when they keep replacing dampers.
The steering box adjustment
The GQ and GU use a recirculating-ball steering box, and the sector shaft develops free play with age. Most workshops never touch it. If everything above checks out and there's more than a couple of centimetres of movement at the wheel before the tyres respond, the box is the last piece.
The adjuster is on top of the box, a slotted screw with a lock nut. Loosen the lock nut, turn the adjuster clockwise a quarter turn, lock it, and drive it. Repeat until the free play is gone. Go too far and the steering binds in the straight-ahead and won't self-centre, which is worse than the wobble, so a quarter turn at a time.
If the box is tight at the centre but still loose off-centre, the worm and ball track are worn and adjustment won't fix it. That's a reconditioned box, and we keep exchange units for GQ and GU.
If you've replaced the damper twice and it's still shaking
Bring it to us in Burleigh Heads. We check all seven in the order above with the Patrol on the hoist, and we'll tell you which two or three are the actual problem. Most death wobbles are gone the same day. Call 07 3924 3317.
