* Steering Rack: A worn or damaged steering rack is a common culprit. The rack and pinion system translates the turning motion of the steering wheel into movement of the wheels. Worn gears or bushings inside the rack can create a thumping sound, especially under load during turns.
* Tie Rod Ends: While you mention new axles, tie rod ends are separate. These connect the steering rack to the wheels. Worn or loose tie rod ends can produce a thumping or knocking sound when turning. Even if recently replaced, a faulty part could have been installed or a related component might be failing.
* Ball Joints: Similar to tie rod ends, ball joints connect the control arms to the steering knuckles. Worn ball joints exhibit a variety of noises, including thumping, particularly when turning.
* Wheel Bearings: While less likely to cause a *thumping* specifically, worn wheel bearings can create a rumbling or groaning sound that might be perceived as a thump under certain turning conditions.
* CV Joints (Constant Velocity Joints): Although you mention new axles, the *CV joints* are the components at the ends of the axles that allow for the change in angle during turning. A failing CV joint can produce a clicking or thumping, particularly under load. It is possible that a seemingly new axle shaft may still have a failing CV joint.
* Suspension Components: Worn bushings in the control arms or other suspension components can contribute to thumping noises when the suspension is stressed during turns.
Why new parts don't rule out these issues:
* Faulty New Parts: There's always a small chance a new part is defective.
* Underlying Problem Not Addressed: The new parts might address symptoms, but the root cause remains. For example, a worn steering rack might cause premature wear on tie rod ends. Replacing the tie rod ends alone doesn't fix the underlying rack issue.
* Installation Error: Incorrect installation of new parts can lead to noises and premature failure.
What to do:
Have a qualified mechanic inspect your steering and suspension system. They can diagnose the precise cause of the thumping by performing a thorough inspection, including checking for play in the steering components. Don't attempt this diagnosis yourself, as improperly identifying the problem could lead to further damage or safety hazards.
