I have a 2008 T4R, V6, 2wd with 43k that has a faint but very annoying gear whine in the rear diff. I know it isn't bearings because you can let off the accelerater and it stops, as soon as you reapply the accelerator it comes back. It's VERY dissappointing and the only thing I dislike about my newly acquired Toyota but it drives me crazy. I've checked the fluid and it is full but I want suggestions on which brand/weight/type of gear oil to run to maybe keep the "whine" to a bare minimum? I will change it myself but wanted to know what you folks have experienced.

It is your rear diff pinion bearing and you are covered under warranty until 5 years 60k miles. Mine did the same thing and they replaced my entire rear diff. No oil will stop it as the beairngs are bad and Toyota know this.

Hey-

No whine from the rear Dif here, but I just replaced my rear gear oil with Royal Purple 75w-90 synthetic yesterday. It's supposed to be quality.

Cheers

Some of the 4R's require a additive to be added when you change the oil. I believe there is a label on the diff that says something to the effect of LSD Additive Required if you need it. If your 4R requires it and you didn't put it in you will get a whine...

Jeff

I just changed the oil in F & R diffs in my 04 Limited. I used Amsoil Severe Gear 75w-90. So far so good. The truck drives super smooth now.

KB084Runner, I need to visit my local dealer for sure and have them listen to it since you're saying it's covered under warranty for 5yr/60k miles. But, I don't think it's a bearing simply because when in the throttle at any cruise speed say 50mph or more you hear it whining at a steady pitch. If you let off, the whine completely goes away. I think if it were a bearing it would have a constant whine anytime the driveshaft/pinion is turning.
I believe I likely have a pinion/ring gear shimming or depth problem. That is, the pinion is either too tight or not tight enough to the ring gear They aren't running "true" to each other.
I don't ever look forward to bringing this up to a dealer though. I expect I'll get excuses like "they all do that so there's no problem, etc." I know it's annoying in a vehicle of this quality and expense that it should not have to be tolerated - it should be fixed correctly.
Did your dealer install a new carrier (differential) assemlby or simply "rebuild" yours with new bearings?