Driveline Vibe Diagnosis Help

So insert them into the A+B+C=0 formula. Working angles that 'face down' are positive, working angles that are 'face up' are negative.

A= 4.4 to 6.3 ----\ face down +1.9
B=6.3 to 7.9 ----\ face down +1.6
C=7.9 to 8.2 ----\ face down +0.3

A+B+C=0
(+1.9)+(+1.6)+(+0.3)=+3.8

You need to increase the working angle at C by 5 degrees so it becomes an 'face up' \___ working angle of 4.7. Shim would be thick side forward.

The new math would be:
A=4.4 to 6.3 face down ----\ +1.9
B=6.3 to 7.9 face down ----\ +1.6
C=7.9 to 4.7 face up \___ -3.2

A+B+C=0
(+1.9)+(1.6)+(-3.2)=+0.3

...remember, 'face up' angles are negative in the A+B+C=0 method.

Everything's kind of approximate.
Adjust C and B changes, so the math changes...
The result will not necessarily be what the math says it will/should be. Might take a few attempts; re-measuring and refining the angles.

 

Gentlemen - So is this thread only for folks that have installed aftermarket lift kits in their 3rd Gen Tacoma's ?
I have a bone stock '17 Taco TRD Sport DCLB that has had a "noticeable' to "significant" seat vibration @ 48mph since about 2,500 miles (4-1/2 years ago) - no amount of wheel balancing and tire rotations have changed the seat vibration . . . if this string only deals with lift kit vibes, I will bow out.
Appreciate your input . . .

 

if you google tacoma driveline vibrations there is an even better thread on here about the struggles of driveline vibrations. There really isn't a one approach fixes all.

I would start with reading this https://www.tacomaworld.com/threads/drive-shaft-vibrations-solved-step-by-step.244535/

 

im no expert, this is why im trying to get help on the forums for my issue.. but like a2lowvw says, there isn't a one approach fix all.

one thing i will add, alot of tacoma guys are buying custom 1 piece drive lines, instead of the OEM design of using a carrier bearing, and almost 2 independent drive lines, adding all these extra angles... toyota engineering has to have their reasons, but to the caveman mentality, its questioned back to their roots.

there's alot of possible fixes.. wheel balance. wheel alignment, wheel spacers... shocks, wheel bearings. suspension parts. questions start when modifying truck height.. lifting.. using carrier bearing drop kits.. im thinking about now a 2 degree shim for my rear end.. there's endless of possibilities.. and any one of them might cure, or might take a combination of parts to fix it. or i could go back stock. lol

 

todays update, i found some steel 2 degree shims for the rear leaf pack. but i decided in the effort of really finding the issue, i decided to go at this CB operating angle. by adjusting the height. i did the 180 degree flip, and i added 1 5/8 galvinized flat washer, and it got my CB operating angle at 1 degree flat. cool.. im still going to test drive, not expecting too much good change.. but my weekend project will be those axle shims, and which will still change this 1 degree CB i just got..

 

Don't forget, there's another dimensions to consider; side-to-side. If you don't confirm it's straight or your rear has thrust you're not acounting for...to borrow a term, you will be 'chasing ghosts'.

 

in reguards to alignment.. im squaring it up to the factory mounting location... you know centered.. not too left or too right, and so forth.. i just took some pics.. still got mild vibes 55-65mph still.

my next step is prolly the 2 degree axle shim.

 

any tips on how to check this? it wasn't a easy find on youtube, but i haven't invested much time into this yet..

 

I checked mine with a string and an extra set of hands. Have one person hold the string on the u joint at the pinion and pull it tight holding across the center of the u joint at the trans output and see if the carrier is centered.

 

3D laser level, string line, plumb off various points of the shafts and record there position on a level floor. You can use the latter to do axle hubs too, and determine if it's square to the shaft(s) line.

 

interesting.. well, can you explain to me the various points and record from level ground.. how do you check horizontal dimensions... i could see how a laser level would work, hrmm.

 

If you're at 1 degree for A, I would just get the pinion slope to equal the first shaft slope. After that any un-trueness could probably get worked out in a +/- 1 degree shim; which is a process you might have to do regardless, for the unforseen...like axle wrap.
How much lift do you have again?
A 3"(lift amount)vertical change over 4'(driveshaft length) is about 3/4" diagonally. In other words, the slip spline is 3/4" further out. The looser fit can induce vibration.
All kinds of things you can geek on...
Have you confirmed it's a second order vibration isolated to the rear driveshaft by driving without it? I say 2nd order, because they might indicate driveshaft angles; 1st order would be rotaional balancing.

Lots you can geek on with this stuff... lol.

 

Just reading through this post now .
Keep in mind these angles need to be checked with all 4 wheels on the ground .
Here is another fantastic video on how to properly get your driveline numbers . Watching this short video should help with accidental errors made when calculating operating angles .
https://www.youtube.com/watch?v=f1m-Fh5kiRU&t=44s

 

I have that as well.

 

i don't have any updates right now, other than i have more shop talk.. i know it may be a combination of things causing this vibration, but during inspecting of my drivetrain, ive noticed where i push and pull vertically, i notice some questionable play in this bearing, or the transmission output shaft. the seal isn't leaking. would this/could this cause vibrations? i would love to see a parts diagram.

 

I'll put up a longer post when I have time, but here's the gist: Driveline shake, stock truck, 3 times back to the dealer with no resolution. Front joint 3.6° down, center joint .1° down, rear joint 2.1 to 2.4° up. Spicer recommends 1 to 1.5° for the front joint on their website so I dropped the trans mount .5" which brought all of the angles in line. Removed the mount, cut and shortened the legs, migged it back together. Many pictures and video to come.

No more vibration!

 

if you have play in a u-joint I would address that before doing anything else. To determine if it is the u-joint I would pull the drive shaft and put the yoke in a vise and recheck for play. If you have play replace the joint. if you don't have play continue diagnosis.

 

i dont' have any u joint play, front or rear.. the rear flange to the diff is good... i only feel play near the red arrows i pointed to. or, i can feel movement near the red arrows by making movement by putting hands on the ujoint carriers and muscle.

and dual port, very interested in your details please.

 

I just installed Bilstein 5100's all the way around and added an Icon 1-1/2' AAL. Ended up lifting the front around 2" with 1/2" of rake in the rear. Truck developed a vibration that cycles (not constant) between 40-50 mph. When I get to highway speeds, it's either gone or happens at a level that I can't pick out from the regular road vibrations. I can live with my vibration if I know it won't cause a premature failure. But that's the thing...How do I know? I have looked into shimming the carrier bearing. Reducing drive angles is hardly ever a bad thing. I can appreciate how thorough everyone is being on this post. Interested to see what you find cures your problem. Happy hunting.

 

Hey Don. Sounds like the front diff needle bearing. Easy way to tell, put the truck in 4hi and see if the vibe disappears. If it does it's the needle bearing. Look up ecgs bushing replacement. Hope this helps.