Vehicle details:
2005
V8
SR5
AWD
110000 miles

Don't know of the TC, rear/front Differentials have ever been changed.....

I know shame on me...

The tranny had a flush and fluid change around 15k miles ago.


EDIT: transmission shifts fine. vehicle goes in and out of 4lo like it should. Center dif locks up w/ no problems....


Symptoms:

Whine sound coming from who knows where. Happens while in gear only. More prominent when center diff is locked up and in 4lo. noticed towards the end of a 3k mile all highway road trip averaging around 80mph.

Its not a high pitched sound at all.. no hard metal on metal clanking or the like. just a small whine that becomes apparent around 10mph and increases its pitch as speed increases. Accelerator pedal has no relation to noise meaning that if I go to decelerate; the whine is still there at its relative speed so engine RPM's have nothing to do with it.

I'm thinking its a final drive issue and have some Mobil 1 75w90 on the way w/ new crush washers.

If its not this, what else could it be?
Do U-Joints make a whine?
Wheel Bearings?

I don't think its wheel bearings because its sounds to low pitched...

Thanks in advance for the help guys hopefully I painted a nice picture for the Gurus!


-Nuc

Start simple and check the fluid levels in the TC and diffs.

That's about as much help as I can be, but hopefully you'll get more.

I will def check once the new gear oil gets here.


What I was thinking that after a road trip; the alignment might be a little out of whack but the runner is not pulling from one side to the other. I did check PSI's and do a visual inspection after the OP and all checked out well. I am able to clearly tell that since I got the car with around 87k miles that the tires have worn quite a bit but would that really cause a more of a low pitched whine with tires worn?


I race motorcycles via road course and it might be possible that I'm being overly cautious/ curious about some stupid noise that normally comes with wear and tear on disposable parts like tires for example....


who knows. I will post back with my findings after I change the gear oil.

Thanks,
NUC

New oil is good for long term wear. I'd think whining, if it was oil related, would only be from low levels. I'd at least check the TC right away. It's not hard to get to.

I would like to add I have similar whine in my 2004 4Runner Limited, Full time 4 wheel drive. I bought it from a mechanic with 62k on it. I can only assume he serviced all fluids at recommended intervals. I have over 90k miles and just had dealership replace timing belt, etc. and had tranny service and fluid changes on front and rear diffs and transfer case.
I did not notice this whine til after fluid changes. It seems to be between 2nd and 3rd gear and goes away (about 25-30 mph). But I got new tires so not sure if imagining whine or it was already there.
I am concerned fluid changes may have removed some varnish if the previous owner didn't change them but I doubt it since he runs his own shop. I haven't been able to get in touch to ask him.
I have read transfer case shaft wears and causes whine at those speeds as well as tranny service loosening up sludge creating problems.
I would appreciate any and all thoughts on the issue. Thank you everyone.

I forgot to mention tranny service was drain and fill, not full flush. Being physically disabled I can't do the work myself and the mechanic I bought it from couldn't do service because he didn't have "Toyota tool" needed. And the "special Toyota fluids".......

I have spent a fortune at the dealership and am hoping this is normal wear and not an expensive fix but it is driving me crazy. Trying to avoid anymore dealership visits for awhile, money is tight after all the work they did. Coolant flush too and brake flush. Only thing left is power steering flush. Didn't mean to go off topic. What would cause the whine?

Thanks again

Just saw previous owner at shop. Front, center, rear diff's fluids were changed at 1500, 30k, and 60k. Tranny wasn't til now at 93k along with gear oils. Manual doesn't specify change intervals but he agrees with local Toyota dealer on 30k gear oil changes and 90k "minor" transmission service.

He test drove it after checking fluid levels. Says I'm hallucinating whine. Says just a full time four wheel drive with close to a 100k miles of wear.

Sounds good but still skeptical. I would like to know exactly what is wearing. I may be over thinking but I need this 4r to last few more years at least.