kzh138 4wd hum sound

2000 model 4wd, above 60km/hr we get a low toned hum that gets louder with speed.
Not a diff whine sound , but more of a dead wheel bearing sound. Same sound regardless of gear, even in neutral rolling alone its the same

Replaced new tires , new wheel bearing. mechanic says diff or transfer case.

Anyone experienced this? or had to remove front diff? is its super difficult?

Replaced both front and rear wheel bearings?

The other bearing at front that can wear is the rhs driveshaft carrier bearing where it goes through the frame rail.

Oh and also worth checking transmission and engine mounts. If the rubber is completely gone in mounts you can get resonances rumbling into cab.

thanks for the reply

So wheel bearings have been done, front and rear on left side.
I will check the one on right side, i wasnt aware there was one there

Sorry, that reads like you’ve done wheel bearings only on left side. ? The rear bearings on these Hiaces often don’t get done simply because they can be an absolute beast to remove. They can produce noises not normally attributed to wheel bearings. My last one produced a whine exactly like diff whine and only on overrun - exactly like a diff. I put up with it for 5 years assuming absolutely that it was diff. Made absolutely no noise, whirring nor had freeplay when checking by hand with wheel raised.

Oh yeah, another relatively common potential source of whirring is chain in the transfer case.

Pete_nz is spot on here.

Basically anything with a bearing can cause a hum and anything with a fixed support can transmit the sound, as can a failed damping support.

Hopefully you can narrow down the location by moving a passenger about inside the vehicle. A crude stethoscope (arms-length long piece of rubber hose you can press to suspension mounts etc with the other end near your, or someone elses ear) can work. From the driving seat it can be difficult to pin point a noise towards the rear of the van. I had a shot rear engine mount that caused a lot of noise, but only on over run.

Might also be worth getting the van on axle stands and checking all the usual moving parts for play or contact where it should not be. Also check all your fluid levels and for any leaks or parts getting warmer than they should.

Good luck!

p.s. I’ve not removed the front diff, but it’s fairly busy and complicated in that area. In addition to the RHS carrier bearing there are several rubber mounts (called stoppers) for the front diff (and support brackets). These are fitted both sides and front and back of the diff with a lower and upper to each set so 4 lower and 4 upper, plus a dynamic damper (depending on model I think). It’s all covered in the EPC, but this isn’t where I’d start but I would include these when testing all the running gear.