Drive Shaft Vibrations Solved Step-by-Step

Yeah... I think it's overlooked here.

Hmm, guess you work on something else.

 

Thank you all for the feedback! I appreciate the expertise and experience that you all bring to the table!

Brandon### - Rear consists of All Pro Expedition leaf springs, Bilstein shocks, ToyTec shims, for a 4" lift. Front consists of RCD 4" lift set, Icon coil over shocks. Added All Pro front and rear bumpers, rock sliders with fill plates, and custom bent front headlight loops each side. Warn 9.5XP synthetic winch, Piaa fogs, Pro Comp 17x8 wheels, BFG LT285/70/R17 All Terrains (kinda noisy at 60+). Truck is built for expedition (down dirt road to trout stream, out Baja road to coastal lobster spot, etc).

2-piece versus 1-piece drive shafts - yeah, WTF, who came up with this two piece crap anyways? We're not driving super extended flat bed 18-wheelers here, it's a Toy for goodness sake. Whatever. It's my first 2-piece shaft lift, and darn do I feel shafted.


X-axis of the carrier bearing – yup, I did inadvertently omit that step in my write-up, thank you for catching that! I took my carrier bearing bolts in and out so many times during the fine tuning phase that lining things up became second nature. I personally tightened the two carrier bearing bolts to almost snug, then simply beat on the drive shafts and bounced them up / down / left / right a couple of times until the carrier bearing fell into a natural position. The first time I tightened the carrier bearing bolts I noticed that it tended to skew the bracket ever so slightly as I tightened one side, then the other, so I loosened, paid attention to holding the bracket in place, and carefully snugged each bolt down (no, to torque wrench, just “grrrrrrr, GRRRR” tight by hand). Just went out to parking lot under truck, used the string to zerks trick, lines up nicely. Good method Badger, thanks for that. One comment I do have about “perfect alignment” though. I just now loosened the bolts, slide the bearing as far as possible to one side, tightened, and test drove. Not much change. Tried shifting to the other side extreme, nope, didn’t feel a thing. In theory it should induce vibration, but I didn’t feel it. Weird. The most important thing I keep discovering is that 1) the driveshafts DO NOT want to be perfectly in line, 2) the angles, within reason, aren’t that incredibly complicated or critical, and 3) tuning tuning tuning with those carrier bearing shims are what it’s all about. That said, yes, mine are in line along the X-axis. Just makes me feel better that they are.

Measuring the rear diff angle by placing the gauge against the rear axle housing – yeah, that’s probably not the most accurate place in the world. I get about a tenth of a degree or two difference, depending on if I wiggle my fingers while trying to hold dead still against that “flat” spot I pointed out in the photo. And looking at it, that portion of the axle housing could easily be off almost a full degree from the actual U-joint yokes. Although I need to point out again, it’s not that complicated or critical. As long as it’s between, oh, let’s say 0degrees and 3degrees, it should work fine. I crawled around under a bunch of stock Tacoma’s at my local dealer’s lot (midnight with a flashlight, girlfriend keeping watch), measuring different “stock” angles, and they were all within a few degrees of each other, somewhere within the 0-3 range.

I got way too caught up in trying to do perfect math, where to measure, how to measure, did I measure correctly, etc. The take away message is it doesn’t matter if it’s a bass guitar or a mandolin, it’s not the exact length of the neck that matters, it’s if your strings are in tune to what you play. (I’ve never played a guitar in my life, so apologies to true musicians, and mechanics for that matter. I just drive the damn thing.) Advice to fellow noobs like me, concentrate on that pocket full of washers.

Thanks again for all the feedback!

 

x2 - this immediately fixed any vibe issues

 

Wicked 2007, Cummins6Speed, and all other proponents of the one piece driveshaft: absofuckinglutely correct! A one piece shaft automatically splits the difference between the transfer case / transmission and the rear differential, and my huge post about having to tune the two driveshafts to become one harmonious driveline becomes a completely unnecessary waste of time. Simple, clean, single piece driveshaft solution, has worked for years and years. Toyota isn't the only modern manufacturer to go with the newer two piece setup, and it's seriously a pain in the rear. ( huh, bad pun there, sorry ). Not a good thing. I can't see any advantage to having the OEM two piece, other than shims and washers being way cheaper than a driveshaft. When you take into account the number of hours I spent figuring this stuff out......... shoulda gone with a one piece probably. If you have more time than money, fix your two piece. If you simply want to write a check and have it fixed immediately, go with a single piece.

 

http://www2.dana.com/pdf/J3311-1-DSSP.pdf

page 6, 7, and 21

 

Well waddya know… Badger’s Dana pdf, page 7 (pdf sheet 7, document page #4), Changing Safe Operating Speed…. “Changing the installed length of a driveshaft [to increase safe operating speed, Safety Third] will require bla bla multiple shafts bla etc center bearing bullshit etc bla bla.” Thank you Badger, clears up why so many new manufacturers are going with two piece shafts, it’s to increase driveshaft speed and thus safety. Still royally sucks when your teeth are colliding from driveline shakes, but at least we can give a slight nod to Toyota and other makers for at least having good intentions. I might stand corrected on my post to Wicked about one piece. Thank you forum members, every day an education.

 

It's not to say that a one piece can't work, but the engineers at Toyota are not stupid. Things are not as simple as they sometimes appear. It used to be that trucks were generally low speed vehicles, but now people buy them and want to drive 90. If you go through the numbers, you will see that the Toyota shaft gets close to trouble if pushed too far in a single configuration. I'm pretty sure that's why they opted for the more expensive double shaft. Mine (double) is properly aligned and has no vibration from 0 to 85, which is as far as I have pushed it.

 

Great write-up OP. You correctly identified a few of the compounding issues that result in drive-line vibrations.

As a mechanical engineer, I can't help but want to explain why/how some of those issues occur for anyone that is interested.

The OP eluded to the concept of constructive/destructive interference, illustrated in figure 1.

Figure 1. Constructive and Destructive waves

This concept is important as it is the underlying phenomena responsible for resonance (figure 2). Exciting an object at a specific frequency (resonance frequency) can result in extreme perceived vibrations - vibrations powerful enough to work bolts loose, fatigue the material, etc.

Figure 2. Example resonance frequency

It can be seen in figure 2 that a small change in amplitude can result in a huge change in the amplitude of motion if that change is [causes excitation] near the resonance frequency. Thus, when the OP talks about small changes making a huge difference, this is why. Of course, a system as complicated as a driveline will have multiple resonance frequencies with various amplitudes (see figure 3). Thus is it possible continue making adjustments and move from one peak, to a valley, only to reach another peak, even though you made adjustments "in the same direction".

It is possible to use the idea of destructive interference to eliminate (or nearly) drive-line vibrations. This was experienced by the OP when he finally hit the sweet spot and experienced a "perfectly smooth" ride. Changing the weight, orientation, material, support structure, etc. can all effect the resonance frequency (or corresponding modal points) of a system. The right graph in Figure 3 shows an Fast Fourier Transform (FFT) of the time data (left), which shows the three resonance frequencies and two modal points.

Figure 3. FFT of time data illustrating resonance frequencies and modal points

The modal points are the valleys in the FFT (right graph). This is the frequency that causes the most destructive interference, thereby causing the least disturbance or amplitude of motion of the object (desirable for a driveline)

I had a lab once that let us prove these concepts to our selves by exciting objects we brought from home and finding the resonance frequencies and modal shapes. I performed this vibration analysis on a cocktail mixer.


Figure 4. Apparatus sketch


Figure 5. Cocktail mixer dimensions


Figure 6. Cocktail mixer reference/measuring points for analysis


Figure 7. Cocktail mixer transfer functions (FFT)


Figure 8. 2D plot of modeshape of the cocktail mixer at 495.6 Hz, 4th resonance frequency


Figure 3. 3D plot of modeshape of the cocktail mixer at 495.6 Hz, 4th resonance frequency





I hope somebody found this as interesting as I do Take care.

Hunter

 

<-------- mind blown

 

Whoa...you just brought this thread to whole new level

 

Thanks for posting this, as I'm having some small vibe issues on take off.

Jim

 

Uh...... yeah...... Did I mention a hand full of washers? I got so caught up in the theoretical measurements behind WHY my vibes were happening that I got frozen into inactivity. I was afraid to try anything at all because of all the helpful but conflicting advice out there, I had absolutely no idea in which direction to even start. My nerd brain was overpowering my mechanic brain, although I have to admit I really dig Badgers and Hunters info....

Area52, usually take off vibes are caused by the wrong rear diff angle, meaning you might need rear leaf spring shims. Think about it, the only things that change from stop to take off to running at speed are driveline torque (Badgers article) and axle wrap (entire rear axle rotates up and clockwise when looking at your drivers side rear tire from the drivers side, as if you were changing that wheel). If it's only a takeoff vibe, and it goes away at any semblance of speed and never returns, in my experience it was the rear diff angle being changed by axle wrap torque. I messed with tons of carrier bearing adjustments trying to tune the system (Hunters article), but nothing helped until I measured and corrected the rear diff angle, with shims.

 

I installed shims when I lifted it last week.

In the last few days, it's much reduced, so I'm thinking the suspension settled, so it may self resolve or only need a very minor tweak.

 

Update: A different method, probably easier and better

Let me start off by saying badger is a frickin’ Rock God from Mars when it comes to this driveline crap. I mean really badger, why let all of us newbies fumble around, you’ve got every answer and every angle covered! A BIG NOD AND THANKS TO BADGER for infinite wisdom. I was digging around another post when I came across some extremely useful information, that I feel was getting buried amongst page after page of responses. I want to quote badger here, so it’s a little more accessible. I didn’t ask badger first, so hopefully this isn’t creating bad forum blood, but again all credit goes to him for the following:

Quoting badger:
“Here are the three possibilities [for fixing this driveshaft shudder sh*t]:
1. (my [badger’s] preferred method and Toyota's method) Align the TC output shaft and pinion shaft to be parallel. On most trucks with well designed lifts they will already be correct. Then drop the CB a small amount until the two driveshafts almost form a straight line (less that 1 degree). This geometry puts the 1st and 3rd joints canceling. Joint 2 is (near) zero. Side effects > none.

2. (Beefy CB drop) Align the TC output shaft and pinion shaft to be parallel. On most trucks with well designed lifts they will already be correct. Then drop the CB until the rear shaft forms a (near) zero operating angle with the pinion shaft. This geometry puts the 1st and 2nd joints canceling. Joint 3 is (near) zero. Side effects: greater operating angle at the TC joint will cause faster wear and may limit high speed operation. DL clearance is reduced.

3. (Spicer diagram) Raise the CB until the first shaft forms a near zero operating angle with the TC output. Adjust the pinion angle to be parallel with the first shaft. This geometry puts joints 2 and 3 canceling. Joint 1 is (near) zero. Side effect: Driveline clearance will be increased. A custom crossmember will be required to relocate the CB. Operating angles at Joints 2 and 3 will be increased causing accelerated wear and possible high speed limitations. This method is commonly used in trucks with long shafts and little lift where the angles are not a concern. Most commercial trucks are set up this way.

Note 1: Joints should never run at a dead zero operating angle. That's why I keep saying "near zero". A joint that operates at zero will not rotate on it's needle bearings and will wear in one spot on each post/cap. The bearing must operate at a slight angle to move lubricant and to wear evenly around the post/cap. Joints can, and should run at a zero relative angle when parallel axis are established.

Note 2: Toyota did not make any mistakes in the design of this drive shaft system. They chose option one for the same reason I chose it. They used a 2 piece shaft to eliminate critical speed instability, and they designed it for the least side effects. My only complaint, or perhaps question, is why they used such a wimpy carrier bearing. I don't know. I think some of the issues stem from that, and I plan to change that on my truck eventually. For mild lifts of 3" or less the geometry can pretty easliy be returned to optimum by understanding the reasoning behind the geometry.

I think that's about all there is to say on the subject.”

End badger’s awesome wisdom quoted.

Turns out my originally posted solution was something along the lines of badger’s Solution #3, in that I had aligned the rear diff pinion darn near (0.1degrees) perfectly in line with the second shaft, then “tuned” the carrier bearing drop. Worked, but I was a little concerned over long term wear, as badger pointed out.

So, I decided to try badger’s Solution #1, along the lines of the OEM Toyota alignment. Step by Step:

1. First, I measured the transfer case pinion angle, and zeroed my digital gauge against that measurement. After getting multiple different readings from trying to use a socket on the u-joint caps (mine have a lock ring over the cap that makes the socket rock), trying to find a flat place on some part of the u-joint yoke that equaled the true pinion angle (couldn’t find any that weren’t a degree or two off) etc, I finally just placed a flat steel bar against the pinion, uh, what’s that part called… plate? See photos #1 and #2.

2. Next, with the gauge at zero (if your gauge doesn’t reset to zero, don’t sweat it, just remember the angle it measured), I slid back to the rear pinion and measured from the same place, that flat, uh, plate, and read that angle. Before I messed with any mechanical changes, I noticed that my readings were damn near exactly 4degreees off of each other (with the transfer case pinion set at zero, the rear diff pinion read 3.9degrees on the gauge). Remember from my first original post I had installed 4degree leaf shims. AHA. I f*cked up! By exactly 4degrees, as it turns out. Upon further reading the other awesome but lengthy post, it was either badger or maxamillion2345 that had mentioned the All-Pro expedition leaf pack didn’t need a shim. Double f*ck. Called All-Pro, sho’ ‘nuff, no shim required, their leaf pack doesn’t significantly change the rear diff angle in any way. Triple f*ck for stupidity on my part. At this point I’m holding Stupid Gun to my Loser forehead….. Whatever. Live and learn, hopefully. Promptly threw the truck on the lift, yanked those shims, and now both pinions read pretty much the same. See photos #3 and #4.

3. Thirdly, now time to mess with my favorite carrier bearing. Promptly when out and purchased an air tool for my socket set, my wrist was getting tired. (I have a hot girlfriend, wrist isn’t used to that much repetitive motion). Anyway, put the digital angle gauge on the rear shaft, set it to zero, and measured the front shaft to see the difference. Following Badger The Great’s advice (is my nose brown enough yet?), I dropped the carrier bearing about, oh, 10mm I think, using the ToyTec spacer I had and that original hardware store washer. Drove it, stuck another washer in, drove it, removed the spacer, drove it, messed with it, etc, until it’s fairly smooth. A bit of vibration at high speed, over 60mph, but right now both driveshafts are to within 0.1 degree of each other, so I have a bit more messing around to get them more like a full degree apart rather than a tenth of a degree, to lube the needle bearings. See photos #5, #6, and #7.

So here’s my point: while my original post worked, on a couple of different vehicles, it appears I was choosing to align the wrong parts, from a longevity standpoint. As badger pointed out, Toyota is not stupid, and it was out of frustration and ignorance that I had bagged on them so heavily. This second method took a total of 45minutes, including some road test time, incredibly easy, productive, and fast. Wish I had done it back in March when I originally lifted my truck……

In reading other posts, there seems to be tons of confusion over the terminology (TC output shaft, TC pinion, TC shaft, first driveshaft out of TC, etc etc), and certainly where and how to measure. I read lots of frustration and confusion amongst the posts. Hopefully this second method, and the enclosed photos, will help.

 

Good job OP

 

x2 pretty sweet!

 

Good job. Don't forget to line up your drivelines (carrier bearing) on the x axis as well. Badger's tip about a line tied between the zerks and then lining up the carrier bearing u-joint makes it much easier. I did essentially the same thing but hadn't thought of using the zerks.

Unfortunately, as Badger also mentioned, the carrier bearing is pretty pathetic on these. Mine is worn and loose and so I don't think I can completely eliminate vibration because of that.


http://www.tacomaworld.com/forum/2n...-driveline-vibration-free-14.html#post4926177

 

I'm glad my posts helped. I pretty much avoid the subject now, and you can see why by reading through that thread. I've been hiding ever since . Now the OP has flipped over the rock I've been under. My posts run from about page 6 through 10 or 11 if anyone wants to read it all: http://www.tacomaworld.com/forum/2nd-gen-tacomas/153050-just-fixed-driveline-vibration-free-6.html

The string on the zerks works well, Just rotate the driveshaft till the zerks are straight down. If you don't align the CB side to side you can get compound angles which make the process of finding the vibration much harder.

I used a flat bar extended from the flanges just like the OP, except I used a little 4" visegrip to hold it on.

Fixing this problem is pretty simple, but you have to take accurate measurements. You are working with fractions of a degree in some cases. That was something I just couldn't seem to get across.

Now I'm going back to >>

 

Sub'd

 

Sub for sure on this. Looks great