I just noticed this afternoon. It's an '02 Patrol GU A/T with an aftermarket 4x4 system from HPI (Hummer Philippines, Inc.) consisting of the shifter, manual AVM front hubs, front driveshaft and indicator relay.

I tried testing the system twice. Once with both hubs locked and once with both hubs unlocked. Also tried shifting in different A/T gears but as per manual, shifts should be done in neutral. Hand brake engaged, right foot on brake pedal.

Shifting from 2H to 4H and back is uneventful.

Shifting from 4H to N, N to 4L, and vice versa produces some very nasty grinding/meshing sounds and the transfer lever is very hesitant to go in. But when it does go in, there's a loud thud.

Once in, the grinding/meshing disappears and the vehicle is driveable...I also tried shifting it with the engine off and the A/T lever in Neutral. Not surprising, there were no grinding sounds.

Any ideas?