* Front Axle U-joints: These connect the driveshafts to the axle shafts. Worn or damaged U-joints will create a grinding noise, especially under load (like turning the wheel in 4WD) and can lead to a binding or hobble. This is a very common problem in Jeeps, especially older ones.
* Front Differential: Problems within the front differential itself, such as worn gears, a broken pinion gear, or a lack of lubrication (low gear oil) can produce grinding noises, especially under stress like turning. The hobble could indicate binding within the differential.
* Transfer Case: While less likely to cause a steering-specific issue, a problem with the transfer case (like worn gears or a binding mechanism) can contribute to overall drivetrain resistance and potentially amplify the noise from other failing components.
* CV Joints (Constant Velocity Joints): While less common on a Wrangler's front axle (especially a 1993 model which likely has U-joints), worn CV joints in the front axles *could* contribute to noise and binding, particularly under stress.
Why it only happens in 4WD and when turning the wheel all the way:
When in 4WD, the front axle is engaged, putting a significant load on all its components. Turning the steering wheel all the way increases the angle of the driveshafts and axles, putting even more stress on the U-joints and differential. This increased stress reveals the underlying problems that might be less noticeable in 2WD.
What to do:
1. Check the front differential fluid: Low or dirty fluid is a major contributor to grinding and binding. Check the level and condition of the fluid. If it's low, dirty, or milky (indicating water contamination), you need to drain, flush, and refill it with the correct type of gear oil.
2. Inspect the U-joints: Carefully inspect all four U-joints on the front axles. Look for any play, looseness, or damage to the boots. You might even be able to feel the roughness by hand (but be careful!). Worn U-joints usually need replacing.
3. Listen carefully: Try to pinpoint the location of the grinding noise. Is it coming from the front axle area, more specifically from one side, or does it seem to emanate from near the transfer case? This will help diagnose the problem.
4. Professional Inspection: Given the age of the vehicle and the complexity of the drivetrain, it's best to have a qualified mechanic inspect your Jeep. Trying to diagnose and repair 4WD problems without experience can lead to further damage.
Ignoring this issue could lead to more serious and costly damage. Get it checked out soon!
