Harmonic Vibrations

[0101fam]

So on my 2001 Land Cruiser it has a harmonic vibration that I have been trying to solve. Harmonic is most noticed 50-60mph, doesn’t matter if on throttle or not.

I believe it’s my front differential from everything else I’ve replaced. Started with what sounded like a pinion whine noise so decided to tackle the easy stuff. Wheel bearings, needle bearings, cv axles, both driveshafts, and all balljoints/tie rods. Each part replaced definitely helped a little.

Next step is to either try new differential bushings, but wondering if I should just go ahead and either rebuild or replace front differential.

 

[3_puppies]

try removing the front driveshaft, you will need to engage the center diff lock

 

[0101fam]

try removing the front driveshaft, you will need to engage the center diff lock

I’ve tried that, and removing the rear. Removing the front makes the pinion whine go away but harmonic still there. Need to pull flanges, shaft and test but haven’t had time yet.

 

[LJE]

Welcome to my hell.

Now, hopefully your problem isn't as bizarre, but, there's a ton of good troubleshooting in that thread!

 

[2001LC]

Spiders (AKA: U-joints) perhaps.

To eliminate engine & AT:
While coasting down hill at 65MPH (shift to N as you idle engine).

 

[0101fam]

Both driveshafts are new Toyota, so U-Joints good. Tried coasting in neutral, made no difference. Also replaced t-case output bearing when resealing just for maintenance

I’ve balanced tires twice, doesn’t seem to change any.

Only thing I notice that is abnormal is that it seems that the hotter the differential gets, the more I hear the harmonic. On a cool morning, it might not even make one sound. This is why I believe it’s pinion bearing or carrier bearing. I have had the cover off diff, gears looked normal, couldn’t feel any play in any direction. Backlash is definitely more than what it should be, but also has 228k on it.

 

[0101fam]

Welcome to my hell.

Now, hopefully your problem isn't as bizarre, but, there's a ton of good troubleshooting in that thread!

Now that I’ve heard your entire thread, starting to get worried haha. My next current steps are new lca, uca, and diff bushings. I still think my issue is with the front diff since I do have an on the throttle pinion noise. Just not wanting to spend the money on a new diff from Toyota so trying to replace things that are cheaper and need to be replaced at this mileage regardless.

My noise is like a rhythmic hum that you could make humming to yourself. Can’t feel it, seems temperate dependent, but not ambient. Start hearing it when the drivetrain gets warm.

I’ve had bad pinion bearings before in a different vehicle, but they only caused a whine. So wondering if I’m just hearing more since it’s an suv and not a truck

 

[LJE]

Now that I’ve heard your entire thread, starting to get worried haha. My next current steps are new lca, uca, and diff bushings. I still think my issue is with the front diff since I do have an on the throttle pinion noise. Just not wanting to spend the money on a new diff from Toyota so trying to replace things that are cheaper and need to be replaced at this mileage regardless.

My noise is like a rhythmic hum that you could make humming to yourself. Can’t feel it, seems temperate dependent, but not ambient. Start hearing it when the drivetrain gets warm.

I’ve had bad pinion bearings before in a different vehicle, but they only caused a whine. So wondering if I’m just hearing more since it’s an suv and not a truck

That sounds a lot like diff noise!

I will say that the 100 series chassis seems to be a tuning fork right around the 40hz range (Toyota even put out an TSB for exhaust resonance at idle centered around 40hz).
If you do the math (depending on gear ratios/tire sizes/etc) you'll find that the front & rear driveshafts are rotating at 40 revs/second right in that 50-60mph range.

That means that any sort of vibration in the driveline is going to be REALLY noticeable in that speed range.

 

[0101fam]

That sounds a lot like diff noise!

I will say that the 100 series chassis seems to be a tuning fork right around the 40hz range (Toyota even put out an TSB for exhaust resonance at idle centered around 40hz).
If you do the math (depending on gear ratios/tire sizes/etc) you'll find that the front & rear driveshafts are rotating at 40 revs/second right in that 50-60mph range.

That means that any sort of vibration in the driveline is going to be REALLY noticeable in that speed range.

Okay definitely the most prominent at 53-58mph. Also makes the resonance at 35 at a slower rate when making a slight right turn when on throttle just enough to “freewheel”.

Going to wait a little till it gets more bothersome and when Toyota runs the next 25% off to get a new differential

 

[0101fam]

That sounds a lot like diff noise!

I will say that the 100 series chassis seems to be a tuning fork right around the 40hz range (Toyota even put out an TSB for exhaust resonance at idle centered around 40hz).
If you do the math (depending on gear ratios/tire sizes/etc) you'll find that the front & rear driveshafts are rotating at 40 revs/second right in that 50-60mph range.

That means that any sort of vibration in the driveline is going to be REALLY noticeable in that speed range.

Update on my progress. New diff installed, pinion noise gone, harmonic still there. Balanced and rotated tires again, no change. Removed front drive shaft, no change. Removed rear drive shaft, no change. Wish I could just pull it and have neither in haha!

Next on my list are new front diff bushings, all new front end bushings, and maybe rear link bushings?