So over Christmas last year I did went down some dirt roads/plantation type stuff but went through some dirty water/mud type stuff (just your average puddle type stuff, nothing too deep and I was gentle and cautious when doing through them)........ anyway my Klugers in the past month developed a noise that I've been trying to narrow down.
So you can hear it essentially ONLY in the cabin about 30-60km/h... it gets faster and turns into a small hum at 100 barely noticeable. It's like a ner ner ner ner ner (faster or slower) and then due to 100kmh is more of a hum then anything. You absolutely cannot hear it outside the car, we've done windows down, drive by's. I've had the car on the stands in gear with all four wheels running.... (not safe enough to do the 30-60kmh) but idling along in drive. All the bearings sound OK. Wobble test seems OK.
I did note at one point when I rotate one of the back wheels with the other on the ground it was smooth if you had your hand on the CV in the middle of it..... but with both wheels off the ground it has like a gap/notch as you turn the wheels. Not 100% sure if thats right, it's a bit of a weird open diff thing so that might be normal.
I could pick anything, front transfer case, universal joints, rear diff, cv's and or bearings......... alot to choose from. Sounds generally travel especially in a AWD..... Be so much easier to find in a FWD or RWD!
My next step is to strap a camera or something under the car and go for a drive see if I can pick it up under the car.... I'm getting close to taking it to Toyota as really you need a lift to really chuck a scope on them and work it out but I don't want to be defeated yet as I do all the cars here always have.
Considering the waters I went through I'm thinking it's a bearing somewhere or the rear diff. I changed the transfer case and the rear diff oils..... one was normal colour, one was black with possible metal bits on it.
I'll post again when I find out wtf it is, I got a recording of the sound I may upload and link as well. I used to own a VE SS Commodore custom cam etc all done by me, this AWD thing is very much a pain for DIY diagnosis.