ROSCOGX470

Tecman, I can’t say I’m experiencing the same symptoms as you. I don’t have an bumps or shifting issues at all. I just notice a constant hum that is faint at 60mph and a little more pronounced at say 80mph. I have 105k miles and as a precaution I may do a couple AT fluid drain and fills, which originally I was against on the whole change don’t change transmission fluids. I called my Lexus dealer and the service advisor said absolutely not unless I tow and I would just be “asking for problems”. I have already serviced the rear diff and transfer case fluids about 30k miles ago so I believe good there. While I had my wheels off for summer switch over I checked for bearing issues and I only noticed a little side to side play and no top to bottom at all.

ROSCOGX470

I put the tire pressure up from 32 to 35 psi and the humming is very faint and almost not noticeable at this point. I don’t really like running 35 psi because I already feel the ride is too stiff to begin with but it did remedy the sound and I probably gained a little better MPG’s which with the prices was the deal breaker.

nuclearn8

I run 36-38 psi with the air suspension on normal or soft... perfect ride quality imo.

ROSCOGX470

I think with the base suspension you need more tire cushion

ErnestPho

Update for those with the whining from the drivetrain while coasting. I took it to a mechanic who confirmed the issue was a worn pinion gear in the front diff. Hope this helps other folks looking for answers!

ErnestPho

Mechanic confirmed it was a worn front diff pinion gear. Options are: replace front diff with a used one, a $$$ new one, or find a rebuild kit.

Car is safe to drive with the noise, but it will likely get louder over time. If it's that annoying (and mine was), best bet is to replace the diff or get it rebuilt.

ROSCOGX470

I may be in the same situation. I haven’t been able to locate source of my slight whine. I was leaning towards wheel bearing but I jacked it up and wheels seem decent…not sure at 60 mph if that changes. Also I know I’m in need of chassis lune in all 6 zerks. What type of money we talking about if it’s the pinion gear?

ErnestPho

I'll let you know. I don't know of anyone who makes rebuild kits, but my mechanic who works on a lot of Toyota SUVs seems to think he can get one. I'll update once I know more.

Acrad

Schematic for front diff

Looks like it sold with these parts as a kit

PN: 4120180195

ROSCOGX470

Thanks Acrad $764.80 for all the parts seems doable but I really can’t judge by the installation and disassembly how many hours of labor it calls for and if it’s something a driveway mechanic could handle.

Acrad

Not something I would personally tackle. I need to have some of this disassembly done in the rear for installation of my locker. I am deferring to a qualified shop.

IanG

I have done a number of differentials and this is not something the average DIY can do. The bearings on the carrier and pinion are pressed on, the depth of the pinion is controlled by shims behind the pinion bearing (every change in pinion depth means pressing on and off the bearing), also the backlash and preload on the carrier is adjusted by shims. If you get the pinion depth, backlash or preload wrong the gears will howl like nothing you have experienced and there will be excessive gear wear.

ROSCOGX470

Thank you, I will differ to the professionals

ROSCOGX470

I will def use an Indy shop that does that work. What would your labor estimate be to say change out a pinion bearing in the front? That’s where the whining sound is coming from if it is indeed the pinion. I see that the entire kit Acrad listed above was over $700 but that seemed to be every part included.

IanG

It has been a while but I would say an experienced mechanic with the correct tools about 3 to 5 hours .... but this is a guess based on my experience years ago.