So I hauled my motorcycle out to Helena, MT back in June from PA and when I arrived in Rapid City I noticed a slight humming noise coming from the rear when I let off the gas and coasted. When I'm on the throttle I don't hear or feel anything unusual just a humming noise when I let off the gas. I took it to my mechanic yesterday and he can hear it but couldn't isolate where it's coming from so I have another appointment in a couple weeks for him to dig a little deeper. Just curious if anyone who owns a Tundra has experienced anything similar or have an idea what's might be going on with the rear. I have about 120000 miles on the clock which is 80% highway miles driving back and forth across country. I'd really like to haul my bike back out to Rapid City SD next week but don't want to be stranded on the side of the road in the middle of nowhere with a blown rear. I do see a new/newer truck in my future but not until the end of the year or sometime next year. Thanks

Early tundras have had issues with rear diffs

Sounds like backlash…

quote:

Originally posted by Patriot:
Sounds like backlash…

What's backlash?

^^^ He means play in the gears in the differential from their being worn out. The problem is that the ring & pinion do the opposite of what you describe, i.e., they make noise when under load and quiet when coasting. A pinion bearing could do that, however. Noise from the carrier or axle bearing is constant, varying only with road speed. All this assumes the noise even comes from the rear diff in the first place.

I wonder if a frequency counter could be diagnostic as to what part is making the noise? Correlating the frequency with the engine RPMs and the gear reduction ratios should show just where in the drive train the noise originates. I have never heard (get it?) of anyone using this technique, but seems like it might be a cheap and easy way to narrow things down.

Toyota issued TSB-0151-10 for rear differential noise. You're out of warranty, but this gives the parts and tools needed. A good mechanic can also do this job.

quote:

Originally posted by ptruck:
Toyota issued TSB-0151-10 for rear differential noise. You're out of warranty, but this gives the parts and tools needed. A good mechanic can also do this job.

Why does stuff always happen when your vehicle is out of warranty? Thanks for the info I'll google it and check it out. My mechanic will be doing the repair, no way Id pay the dealership to do it.

Change your rear differential fluid. It may go away or get quieter.

quote:

Originally posted by Black92LX:
Change your rear differential fluid. It may go away or get quieter.

That might just be a bandaid.

^^^^^^^^^^^^^
It’s a cheap and 15 minute DIY litmus test.
And many times in life a band aid is all you need. Differential work is not cheap. I had a Mustang that the rear end whined the entire 7 years I owned it got quiet with fresh quality fluid but was still there.
Had an Explorer that the whine completely went away with a fluid change because a little water had got in the diff.

If you choose to change your rear axle lubricant consider the Motorcraft 75W140. It is 25 centistokes (thick) and has a proven protection additive. Thicker lubricants can mask noise. The motorcraft is free from polymers as thickeners and will remain thick. A 90 grade lube is 12.5-15.0 centistokes, and may not dampen the noise as well.

Gear whine is caused by ring and pinion teeth interacting under load and off load.

The Toyota axle design is much like the Ford nine inch axle. It can be adjusted. If the gear teeth are worn there is no fixing the teeth, of course.