3rd Gen Poll: Rear End Noise howling when feathering throttle

Been having the howl since ~2k mi. Loaded the bed with 20 river rock bags from menards and the howl vanished. I'm not mechanically inclined and not sure how this would eliminate the howl

 

I think you dampened the resonance. The cause was still there, but you quieted the effect.

 

Did you get up to the speed that the Howling normally occurs?

 

I was able to get up past 54MPH where I typically hear it.
Haha Maybe I should remove one bag at a time to see just how much weight is required to quiet the howl...

 

I am unsure as to what the root cause, but when i had my truck, I swear that I DID notice that if i went over some long rolling bumps on the highway, that as the bed compressed, the howling faded out and came back as the bed decompressed. My next line of action would have been loading my bed up with weight to see if it affected it, but when I really thought about it I realized that if I found it was a driveline angle issue I still wouldn't have wanted to go through the headache of trying to convince the dealer and get them to fix it. And I wasn't ready to pay extra for a driveline shop to fix it and then have Toyota possibly be able to say that "my angles aren't in spec now."

But its worth a shot and easy to do.

 

That would be great. We'll wait here.

 

Great points.

 

Ha I doubt my wife would be happy that her landscaping project is going to take longer because of a TW experiment.

 

Fair enough, but imaging your great contribution to the greater good. The benefits could be ENDLESS!!!

 

By having the truck loaded, you probably weren't feathering the throttle as much. The truck was either pulling itself, or engine braking. Mine doesn't howl in either of those situations.

 

I think it's driveline angles (plus shitty pinion fitting). Smitty said his improved when he added a small lift.

If you add rocks you're also changing the angles, so that still jives. I have some 40lb bags of sand I could toss back there to see if it makes a difference.

As aero mentioned hitting some hills/lumps in the road changes and sometimes eleminates the howl.(I haven't been able to confirm if this is hills related or me letting off the gas pedal on hills.)

 

I focused as hard as I could to not move my foot but I always wondered the same. It just came and went too consistently with the bumps though for me to think it was my foot moving perfectly. Looking back I should have gone out at night, no traffic, and cruise controlled it.

But seriously, I urge others to try putting weight in the bed. It can't take that much if going over some rolling bumps would make it go away.

Part of me would be surprised though if an in spec pinion angle caused it unless there was some loss of preload at which point I would expect the pinion bearing to get bad pretty quick (been there done that on my last truck). If the pinion angle was out of spec a digital angle finder and seriously 10 minutes under the truck would figure it out real quick.

I'd have to check the service manual to see if there are driveline angle specs in there, but if not id usually default to spicer's recommendations. If someone is willing to check theirs, I can dig up the Spicer manual and post it here, it has all the instructions and calculations on how to do it. The manual is online too if anyone wants to search it.

 

That's interesting because when my family of 4 are in the truck the howling in much quieter. I was gonna see if a couple hundred pounds of weights in the bed would eliminate the sound completely. My first rear diff howled when the gas pedal was feathered. But the second one howls at all times just little quieter. 52-58 mph

 

when you change the angle of the drive shaft it appears to make a difference in the amplitude of the noise

 

Smitty, do you think it is possible that the driveshaft is the transducer (like a speaker) for the noise the rear gears are creating. This could be a feasible hypothesis, as I believe the pinion, which is connected to the driveshaft yoke, is one of the components in the ~440 Hz system. Perhaps the driveshaft is being slung by the pinion cogging, and that could be producing noise that we can actually hear. Changing the rear driveshaft angles, could be thwarting the storm. Mustangs had noises like this show up when people changed over to aluminum driveshafts.

 

Could be but I'm at the point now where I don't really give a shit what is causing it, I just want it resolved.

 

We need to find someone with a one piece driveshaft or a cv system and poll them.

 

I asked the question for the purpose of discussion. I have not reached that point and don't know if I will. The rear differential in my Tacoma makes a noticeable noise when feathering the throttle between 55 and 65 miles per hour, but it is not loud and does require me to turn up the volume on my stereo. I have 13,500 miles on the odometer and the noise has not gotten any louder.

Any acquaintance has a 2011 Dodge pickup truck that had issues with the rear differential. He purchased the required parts and for $300 in labor costs he had a professional mechanic, not a technician, at a local transmission/drivetrain shop perform the repairs. His out of pocket was less than $600 and it was repaired right the first time.

My time is valuable to me and I cannot make money if I am sitting on my butt at the dealership. Toyota will not compensate me for lost time and money while I am at the dealership. If at some point I need the rear differential repaired and a qualified independent shop can repair it for $500 or $600, I will go that route. It would probably be more cost effective than trading the truck in on something else.

 

I totally respect what you're saying. I'm in the same boat. Id rather pay for a sure fix than get jerked around for free.

 

Well fuck Toyota.

GD service adviser just told me that the FTS told her that this is a normal characteristic of the the truck. "It's inherent in the design for the DC."

I asked her to refer to it as a design flaw.

All sound and fury though... I told her to keep my case open so when I get a independent shop to repair the "inherent design" flaw I'll have something to reference when I send the repair bill to them. She wasn't too keen on the idea.

I asked her to put it in writing that this isn't a safety issue and she balked; told me to have the service writer at my dealer do it.

I guess the next step is to see what my dealer repair shop thinks.

The frustration for me is my truck has been really good otherwise. I just drove to S. Lake Tahoe and back and averaged 20.6 mpg (calculated) for the 300 miles I drove loaded with my family and all our camping gear (fyi noise didn't change loaded down like that either).