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

I honestly don't know. I'm 100% sure though that the new springs are a revision of the existing spring, meaning, something was changed like material spec, slight geometry change or some other small thing that, when tested, was found to alleviate or at least greatly reduce the resonance. The ones that have this noise that would not get a new spring means that this revision did not work on those units. The isolator and the foam did work though.
Toyota would not take a spring destined for another vehicle and use it on the Tacoma. Easier to just modify, or revise, the existing springs.

 

Also could have tweaked the leaf spring bushing's polymer, lower the durometer (hardness) so it isolates more. Kinda like if you upgrade to poly bushings, you get more feel and vibration.

If Toyota works like our business, they could manufacture a batch (feeder supply) for the initial replacements. Those springs get sent back, checked to see if they fall in line to new specs, install new bushing and repainted to keep the TSB's going to minimize cost.

 

The "upgraded" leaf packs better not squeak when you get them dirty... ppl will be screaming at Toyota for replacements.

That is not a fictional scenario. I was chastised for suggesting peeps use a pressure washer and then maybe some sort of lube spray to quiet them suckers down. Worked every time BTW.

 

With the whine gone and the ECT on all the time mod, I'm finding don't have much to complain about these days.

Just waiting for the next thread to key me into something else I can find annoying. Slightly got into the swish noise when depressing the brake pedal but I keep forgetting about it.

 

After a week and 400 miles or so I stand by my initial assessment of the TSB. Better but definitely not gone.

 

A set of MTs should fix the rest... . I’m not getting mine done until next week. I drove my Yukon yesterday and it has a similar howl/whine at the same speeds, but it’s not as noticeable because the vehicle is church pew quiet.

 

I really hope they extend this TSB to my model sooner than later. I did a trip over the mountains and back this past weekend. Every downhill section I was at 50-60mph due to corners, traffic, etc. That howl gets annoying real quick when you have to listen to it for 15 to 20 secs at a time ha Drove me bonkers and even annoyed the lady. Come on Toyota! Haha

 

Took my truck in Monday to have the TSB fix done, they took my truck apart and then called me and said the kit they received didn't have all the right parts and they would have to order them. So they put my truck back together and hopefully in the next week or so I will take it back and get this fixed.

 

I had the TSB done yesterday. Overall about a 75% reduction of the whine but it also greatly narrowed the MPH "window" in which I hear it. I never had anything done to address this since I first brought this to Toyota's attention, I've just been living with the annoyance for many thousands of miles. Overall I'm pretty happy, if the whine was where it is now when I bought the truck I probably would have noticed it but not been concerned. Also, If I ever want to sell the truck a prospective buyer will not be like "WTF is that noise?". The service writer made a point to tell me that the sum of the parts was about $2000, I think he was just surprised at the extent to which Toyota went dampen a noise. I have severe "dealerphobia" but theses guys have been pretty straight up through and through. They got Toyota corporate/engineers involved way back when and since my case was so well documented, they did the TSB even though I was past the 36k period.

 

No issues with the 4runner. There were other things I didn't like about the Tacoma. Like the weird jumpy throttle and lack of torque. The stalling and hesitation pulling out into traffic. Etc etc haha. But yes the 4runner is great in every aspect.

 

Update: I dropped the truck off first thing this morning to have the TSB done. They called at about 4:00pm to let me know it was ready so I picked it up after work. It was a short drive home, but I think the noise is about 90% gone. I had the radio and AC off and had to really, really listen to hear anything. It was loudest at about 57mph before and now that's about the only speed I hear it and it's VERY faint. It didn't seem like mine was as loud as some of the others to begin with, so for me, I think it will be fine. Hopefully others will have good results as well.

 

Good to hear! At what mph range did it howl before the TSB?

 

It would start around 60-61mph and was loudest at about 57mph and would quit at about 53mph as the truck slowed. It only did it if I let off the gas and let the truck coast. Now I can only hear it right around 57mph and it's really faint. If I wasn't actively trying to find it after the TSB, I probably wouldn't have noticed it. With the air on or radio on, I can't hear it.

 

Replace the rear diff fluid with full synthetic

 

I believe the Factory 75w-85 is already Synthetic and changing it out won't get rid of the Howling as many guys tried.

 

That is the exact range that my truck howls at. 61 all the way down to 53. I think peak for me may be around 57, but its loudest between 55-58 for sure. It used to be just on decel, but it now does it a tiny bit when feathering the throttle. Not nearly as loud as when the truck coasts down though.

Now I just have to hope they extend to 2018 non-TRDs! Or drop $250 or so and do it myself ha

 

Nobody knows if the OE 75W85 is full synthetic, but you would think it is for the price. The weight is only for CAFE standards, you can use 75W90 which will become lighter with use anyway.

So will the 85W, which could be a theory that it lightens up with use and creates a whine like many are experiencing.

Toyota would never say the 85W is the problem, it would be a disaster. I’ve only seen 80W and 85W gear oil for motorcycles, rarely ever in a 4X4 truck.

I changed out fdiff, rdiff, mtrans to Redline full synthetic 75W90 and MT90 at 500 miles. Will soon change the tcase with the required weight full synthetic. Everything is quiet as can be.

 

Was it Howling badly before you changed everything out? Toyota's TSB solution is swapping Rear Springs and adding Sound Deadening Material.

 

Naw man, got M1 full syn in mine. Still does it from 54-60 mph. It's not a gear wear issue. It's a resonance issue.

 

No howling, looks like resonance like edgecrusher says below.

I’m just a synthetic fluids fanatic, that’s all.