TLDR '97 Runner with 220k miles makes a droning noise around 50 mph. Sounds to be like it's the rear end, only while accelerating or maintaining speed. Usually stop when let off gas.
Long post in bound.
Ok 1997 T4R 4wd . Parents owned the vehicle for the last 100k+ miles. I drove it in high school followed by my brother and now I own it so I'll try and give as much detail as I can.
Here what happens. Around 40 mph I start to get a droning/vibrating noise while gently accelerating or maintaining speed (there is no physical vibration that i can feel). It is most noticeable around 50 mph. Around 65 MPH wind and road noise mostly covers it up but it's still there. 75% of the time if I let off the gas and coast it goes away. If i accelerate hard you can not hear the noise. Some days it's louder than others. Some days it quiets down after 60 miles, other days it does not.
The noise is a constant pitch and frequency all that changes is how loud it is. Steering left and right has no affect on the noise. I did notice yesterday, on the interstate that if I turn overdrive off it gets louder.
To me and the wife it sounds like the rear end, but when I road in the back seat I couldn't tell if it was still the rear end or not. I have tried videoing the noise but my cell phone and go pro amplify the road noise so you can't hear it.
Here's what I know about the Runner.
-Has a 2nd hand set of KO2s and take off wheels. The KO2s are not worn much but I don't know the story on them either.
-Recently had a 3" Toytec lift and PCK installed. This was done by my brother so unsure if the noise was there before hand. Even with the PCK the rear axle is not centered under body, I do know that even before the lift the axle was visibly not centered. It has been like that since my parents got it years ago. Never had any issues with alignments though.
-Recently had transmission completely rebuilt after brother got stuck and took it out trying to get unstuck. The shop that did the work was a reputable shop but again, I am not sure if the noise was there before hand.
-Around the 150-160k mark the original rear diff grenaded itself. A used 3rd member was bought and installed by a local shop. I do not know what the actual mileage is on this rear diff.
-Around the 180k mile mark my father and I had issues with rear axle seals.. we replaced them 2 times just to have them leak shortly after. Finally took it to a shop they replaced the rear axle seals 2 times, their 3rd time they started measuring and they claimed that the rear axle housing is actually out of a 2nd gen and they say they put in 2nd gen axle seals. My parents do not remember what shop that was being it was 7 years ago. I don't know if this is true or not. I have been trying to find info on how to to identify what axle is has.
Does anyone have any ideas? My local Toyota dealer says they can not hear anything. I am trying to get it in to another local shop but he's currently booked 2 months out.
So I sort of caught it on video. About 5 seconds in its most noticeable. After that you'll see RPMs drop as I let off gas and the noise stops. There's still a lot of road noise though.