Noises When Turning on Gravel with Centre Diff Locked

[P-Roll Lurker Find all posts View Profile Close P-Roll]

Hi all,

Heard some unusual noises coming from the front end of my prado (2004 VX V6 auto) whilst driving on gravel roads down south last weekend, with the sounds best described as metallic pinging or popping sounds. I could only detect the sounds during low speed (parking speeds) turning movements and only when the centre diff was locked. My question is are these sounds normal? If not, what is causing the sounds and is it causing any damage?

Some theories I have:
+ Transmission windup - Due to the combination of the centre diff being locked and the gravel road surface not being loose enough to allow wheel slip. If this is the case, should I not use the centre diff lock when on good quality gravel roads? A lot of websites seem to suggest using the centre diff lock as soon as you leave the bitumen.
+ Wheel bearings - Mates suggestion for the cause, recommended replacing the bearings.

[stevensr34 Senior Member Find all posts View Profile Close stevensr34]

Transmission-related issue is most likely. You only need the centre diff locked when on rock ledges / extreme mud / soft sand / etc. On any "normal" gravel roads, it is completely unnecessary, and will cause your steering to become heavy, and induce extra tyre (and transmission) wear. Remember that unless one wheel is slipping, you are in a vehicle with constant 4WD anyway!

Simple test for wheel bearings: jack up the wheel that you think has a worn bearing, and when off the ground, try to pull the top of the wheel outwards (and inwards)... if there is any movement at all, then the bearing needs replacing...

Cheers,
Rob

[P-Roll Lurker Find all posts View Profile Close P-Roll]

Thanks Rob, the car seems well planted on most surfaces until it gets really slippery so will hold off on locking the centre diff in future.

Will also check the wheel bearings, seems like an easy check.