Differential hum..

[Hiker865]

[MENTION=167870]Hiker865[/MENTION]
See if the rear crossbar on the roof is loose. I kid you not, I had a noise from the rear over 10. mph. Was the crossbar vibrating. Fixed with some soda bottle shims and rtv.

Nice when it's a cheap fix.

I wish that was the source! the bars seem secure and my wife's car has crossbars with wind noise. This does seem to come from the floor. I am hoping someone would say that it is normal road noise for a 4runner.

New tires went on last week along with diff and transfer case fluid(mobil 1). I have not greased the driveshaft yet.

 

[Hiker865]

replace the rear diff gear oil and see if it changes if so then the diff has some wear issues. this can be from being poorly made or the use ofthe wrong gear oil.. also the rear diff if it is making noise is usually from hard driving of the vehicle the first 500 miles.. also diff gear oil changing should be done at the first oil change if the gear oil is dark or black / smells bad..

When I replaced the gear oil this week, the magnet was full on debris that needed to be cleaned off. The oil was not that dark. It was last changed at 32k miles in 2013. It was previously owned by elderly with no towing or abuse and serviced strictly at Toyota. I hope they didn't put the wrong fluid in. I have a stone driveway and at full lock on startup, I can feel the 4wd bind slightly when turning out of the garage. I thought it may be to a slippery surface.

 

[CruzadoBlanco]

When I replaced the gear oil this week, the magnet was full on debris that needed to be cleaned off. The oil was not that dark. It was last changed at 32k miles in 2013. It was previously owned by elderly with no towing or abuse and serviced strictly at Toyota. I hope they didn't put the wrong fluid in. I have a stone driveway and at full lock on startup, I can feel the 4wd bind slightly when turning out of the garage. I thought it may be to a slippery surface.

the "bind" is just the center limited slip diff resisting. since the V8 is full time 4wd (think heavy duty AWD) it has a torsen style limited slip in the transfer case to allow for on road driving, when in full lock on hard surfaces it'll often skip tires just enough to hear it and or feel it. there is a button to lock the center diff to make it into a conventional part time style 50-50 split transfer case for actual offroad use

Now as for the large amount of debris on the drain plug magnet it could be as simple as the toyota techs not wiping it off when the fluid was changed, all diffs will have some metal shavings substantially more in the first 10k or so miles due to the gears mating but also a lesser amount from wear over time.
Worst case scenario is that the diff is going bad and either the backlash or pinion depth has changed either from damage or improper set up and causing substantial gear teeth or bearing wear. The best course of action is to pull the rear 3rd member out and look at it and turn it by hand. Its very easy to do and will only take an hour or so at most. The hardest part is bleeding the brakes when you put it all back together.

 

[catrains]

This is awd or 4wd ? if AWD and the tires were not rotated and of different wear that does stress out AWD drive train. since most times a 4WD truck the locking of the front /rear axles this is not as much an issue since many do not use 4WD all that often , but still important to keep ALL the tires worn at the same amount to reduce wear.....

5K miles and the magnet full of metal particles well this is NOT good. wear is going on . Toyota may have sucked out the old fluid, instead of draining it .. I would call and ask if they suck or drain the diff gear oils.. many shops suck, MUCH FAST MORE $$$ PROFIT .....

SO did the noise change when you replaced the diff oil ?

on the drive shafts , my new T4R did require greasing . the yoke was not greased .. only give it a couple of pumps that is all it needs .. this may reduce noise...

My family member has this vehicle , a limited AWD 2006 V8 ... problems had was the driver side O2 sensors crapped out @80K miles dealership wanted $800 to change them .. I did it for $200.... the AF O2 is expensive .. now @130K no problems ..I changed one at a time and the 2 codes went away ..

what I found was idling in winter too long to heat up vehicle is not good for these sensors .. the AF sensor runs at very high temps and this did burn out the sensor heater , in the sensor.

good luck

 

[pearlj10]

OP: were you missing a hanger for the exhaust? What was the particular problem causing the hum when you let on and off the throttle? Thanks

 

[Hiker865]

the "bind" is just the center limited slip diff resisting. since the V8 is full time 4wd (think heavy duty AWD) it has a torsen style limited slip in the transfer case to allow for on road driving, when in full lock on hard surfaces it'll often skip tires just enough to hear it and or feel it. there is a button to lock the center diff to make it into a conventional part time style 50-50 split transfer case for actual offroad use

Now as for the large amount of debris on the drain plug magnet it could be as simple as the toyota techs not wiping it off when the fluid was changed, all diffs will have some metal shavings substantially more in the first 10k or so miles due to the gears mating but also a lesser amount from wear over time.
Worst case scenario is that the diff is going bad and either the backlash or pinion depth has changed either from damage or improper set up and causing substantial gear teeth or bearing wear. The best course of action is to pull the rear 3rd member out and look at it and turn it by hand. Its very easy to do and will only take an hour or so at most. The hardest part is bleeding the brakes when you put it all back together.

Thank you for the information and insight. I had my wife drive today while I rode in the cargo area. I have pinpointed the noise to be coming from the rear speaker/subwoofer or window in the corner. I'm feeling very lucky today. I had my ear in the spare tire area and could not hear anything. whew. Never thought about the tech's not wiping off the plug but I bet that is pretty standard given they are probably commission based.

 

[1992BJM3]

I have a 00 4Runner v6 2wd.
Been having a similar issue but at freeway speed. When letting off gas at 55mph+ it’s like a hum/groan/grind noise sounds like a mix of all 3. Could feel it on the driver floorboard. Also noise is present when VERY lightly pressing gas at freeway you have to hit the sweet spot and the noise stay consistent. I have two videos one is when letting off gas and the other is holding the gas very lightly. So I’ve already changed transmission mount because it was bad. Rebalanced driveshaft because it was missing a weight which helped the trans mount go bad from shaking. New u joints. Supposedly previous owner redid rear diff maybe didn’t do it good idk. So I’m thinking the bad trans mount and driveshaft made something bad in the trans by driving it when driveshaft was out of balance and bad trans mount? I used stethoscope and it does sound louder near output of trans where driveshaft slip yolk goes but it’s hard to tell noise can still travel from rear diff. Here’s link to two videos hopefully you can hear it.

00 4Runner Groan/grind/hum when letting off gas freeway speed - YouTube

00 4Runner Steady groan/grind/hum very lightly pressing gas steadily freeway speed - YouTube

 

[alia176]

When a rear driveshaft is at the wrong angle due to decelerating or slightly feathering the gas while going downhil, it makes a GRRRRRRR sound. If the vehicle has a tall lift in the rear, was the angle of the rear DS ever corrected for the lift? This is done with an adjustable UCA or adjustable LCA.

when you're deceling the pinion moves up and puts the rear DS out of the normal running angle. It's an easy fix, usually!

HTH.

I have a 00 4Runner v6 2wd.
Been having a similar issue but at freeway speed. When letting off gas at 55mph+ it’s like a hum/groan/grind noise sounds like a mix of all 3. Could feel it on the driver floorboard. Also noise is present when VERY lightly pressing gas at freeway you have to hit the sweet spot and the noise stay consistent. I have two videos one is when letting off gas and the other is holding the gas very lightly. So I’ve already changed transmission mount because it was bad. Rebalanced driveshaft because it was missing a weight which helped the trans mount go bad from shaking. New u joints. Supposedly previous owner redid rear diff maybe didn’t do it good idk. So I’m thinking the bad trans mount and driveshaft made something bad in the trans by driving it when driveshaft was out of balance and bad trans mount? I used stethoscope and it does sound louder near output of trans where driveshaft slip yolk goes but it’s hard to tell noise can still travel from rear diff. Here’s link to two videos hopefully you can hear it.