Pendulum In the Rear Diff?

I'm 13k mi into my TRD 4x4 OR DCSB, and I already had the dealer warranty replace the rear leaf springs for the squeaking after doing what the truck was made to do; Off-Road. That being said, I noticed shortly before I brought the truck in there was almost like a pendulum swing coming from the back when going over bumps, between idle and 8mph (or so). Only hear it/feel it on solid pavement as being off the beaten path makes it hard to hear and feel abnormalities. After doing the leaf springs That went away. That was at about 7k mi or so. I'm now at 13k mi & the poltergeist is back.

If I hit the speed bump, drainage ditch, etc head on where both rear tires hit it at the same time, I do not hear or feel anything. It is when I'm backing out of my driveway and turning where the back left/right hits the dip first, then followed by the other side is when I get the pendulum swing feeling from the back - almost like as if the spare tire was loose and swinging but I have checked that numerous... NUMEROUS times and its tighter than a... well you get the idea.

My leaf springs are holding up, probably because I've done substantially less time off the beaten path and more mall crawling lately, but that issue is bothering me.

Anyone else experiencing anything like this?!

 

That's a new one. Can you strap a go pro somewhere safe under the truck from various angles see if you can catch any movement? Otherwise schedule a ride with the dealer tech and make sure he rides with you to witness the sensation/sound.

 

Only thing i can think of is the spare.. if it's not snug all the way up could it be giving you that pendulum feeling?

 

Pendulum feeling? Side-to-side or front-to-back?

 

That is tightened down very tight. Its most def not the spare, as it went away with the install of new leafs at around the 7k mi mark.

I was a service writer for Toyota for a while & know the technicians there - that's definitely what will be happening! Now that I think of it, I don't have a GoPro... probably should invest in one already!

 

Side to side sir. You can feel it while operating the vehicle as well as it being audible.

 

How do your springs look? Negative arch?

 

Honestly, I'm unsure of what that means.

 

Take a pic of your leafs and post them

 

Does it go clank, clank, clank with slight bucking until it damps out? I get that over speed bumps sometimes.

Also if I shift into 2nd at lower RPM's and step hard on the gas, the power delivery is like a sine wave and I get the same symptoms except for the clanking sound.

This is my first Tacoma so I don't know, but my last truck didn't do anything like that.

 

No, I get none of those other symptoms. I only get it over bumps and its a few "swings" if you will maybe 2-3 and it stops. Most bumps I am able to recreate the problem, while others I get no reactions out of it. I would say 95% of the time I can anticipate when it will do it or not. Have you done the transmission TSB update yet? That might solve some of those issues you're having with the gear shifting.

 

Fuel in tank shifting/sloshing perhaps

 

Not a bad suggestion, but I get it with a full/half empty/empty tank.

 

Have you crawled under and made sure everything is tight besides the spare? Shocks, Springs, driveshaft, etc...

 

Could be axle wrap he's experiencing .... Icon springs FTW??

 

I have not, I will do so today. Driving over to Ft. Lauderdale from my side of the state today before I fly out to Houston this weekend. Will definitely check all components before I get on the road!

Unfamiliar with axle wrap, I'll do some researching - mind explaining from your end?

 

Axle-wrap aka axle-hop is when the springs bind and unbind in such a way that the axle actually rotates a little bit, which makes weird shit happen. Perennial problem with leaf-sprung vehicles. When it's real bad it can break spring shackles, shock mounts, axletubes, pinions, u-joints, all kinds of stuff. When it's minor, it's just annoying.

 

Axle wrap can also come about from the rear drive shaft binding in the carrier bearing. That bearing is there so the drive shaft and axle can articulate a small amount (move in and out and the axle turns slightly) due to normal design of the leaf spring suspension. Basically the drive shaft moves forward and back a little bit when coming to a stop or taking off from a stop among other things. The shaft sometimes does not move smoothly and then releases suddenly = axle wrap. Sudden release is what you feel/hear as a thump... kinda sounds like a basketball in the bed. Annoying....

I had a mild case of this in my truck, when I swapped to Bilstein 5100s and a set of AALs from Icon and removed the helper spring... problem solved.

 

A lot of the 2016 models apparently came from the factory with loose U-bolts holding the axle to the spring.

Quick and easy to check.

https://www.tacomaworld.com/threads/check-your-u-bolts.397913/

 

The basketball in the bed analogy does not sound familiar at all. I feel like it is loose U-bolts from viewing the diagram and then realizing right before the leaf springs were replaced it was doing it, then when the new leaf springs went in, that all went away for a few thousand miles and now its back.