Drive Shaft Vibrations Solved Step-by-Step

Nice write up btw. If anyone near Houston can help; I'll pay you to do that. I'm mechanically declined.

 

I'm trying to get rid of my vibes. I have 1" blocks in the rear (for now) and have tried the OME CB drop kit and / or using thin washers with no results. I've tried just about every variation of washers and with only 1 thin washer my angles look good to the naked eye. Still getting vibes around 20 mph. I have a Prerunner trd sport btw. Should I get some 2 degree shims and then try again or should i mess with aligning the CB left to right?

 

BacoTacoBro: Well there's your problem right thar! Impossible to do this stuff "by eye". Some form of angle gauge is mandatory.

I've been messing around with 1degree angle changes, just to see the effect on drive-ability, and it's scary how much the slightest change can totally mess your drive line. I've found that lower speed vibrations, if under medium to hard acceleration, are (possibly) caused by rear axle wrap and thus you may need rear leaf shims under those blocks of yours. If the lower speed vibes are there even under the most gentle to medium of accelerations from a dead stop, or they persist while driving down the road under normal conditions at that lower speed, it’s most likely the front transfer case and a CB shim is in order.

Notice this is a total “non-answer”! Without actual measurements, you’re just shooting in the dark. Vibe your way to the local hardware store, get a cheap angle gauge and a metallic flat bar to press up against the pinion flanges, and get some measurements!

To blatantly borrow from and give credit to a certain most helpful geologically challenged mech engineer, and to follow along with the photos on my last post:

Tcase versus rear pinion angle (zero on front flange, measure rear pinion flange)
_____degrees (photos #1 thru #4)

Tcase operating angle (zero on front flange, measure first shaft)
_____degrees (photos #1, #2, and #6)


CB operating angle (zero on front flange, measure first shaft - second shaft)
_____degrees first shaft - _____degrees second shaft = _____degrees (photos #6 & #5)

Pinion operating angle (zero on pinion flange, measure second shaft)
_____degrees (photos #1, #2, and #5)

Is the pinion off pointing up or down?
_____up ______down (photo #4, keep your thumb pressed against the rear flange and with your other hand pull the bottom of your metal measuring bar toward the front of the truck. Watch the angle change: if the number increases, you’re pointing UP, if it decreases, you’re pointing DOWN. If you didn’t get a magnetic angle gauge, you need more hands).

See the photos on my last post for measurement methods and locations.

Awww heck, and yes, I always forget to mention aligning your CB left to right no matter what. String, zerks, etc. Had to get that in before I got reminded a million more times by a certain max….

 

Must be that pesky Canadian twin of mine!

 

Now that sir, was one hell of an answer!!! This is why I love TW so much.

Well I was trying to keep it simple I guess but looks like ill have to buy one of those angle readers and really dig in. Ill see if I can find one tomorrow.

 

Baco: PM me your address and I'll ship you my Cen-Tech digital gauge I just purchased from Harbor Freight. Consider it a gift. When you're done with it, you can pass it along to another TW member.

Turns out the Cen-Tech gauge is only accurate to 0.3 degrees, which would probably work for most people. I'm being over-kill accurate about trying to nail The Perfect Formula to End All Vibes with this drive line vibe issue, so I'm replacing my Cen-Tech with a Wixey WR300, http://www.wixey.com/anglegauge/index.html, which is accurate to 0.1 degrees (see this dude's review, http://www.ts-aligner.com/ts-aligner-jr-lite-vs-wixey.htm).

Update on my Tacoma: super smooth at

TC-1st shaft: 7.6
CB angle: 0.0
Pinion: 6.7
TC-pinion: 0.6 up


That's with a 1deg shim. Going to try my 2deg shim this afternoon and see what happens. Then do it all again when the new gauge arrives. I've managed to get smooth driving with three separate setups now, each one radically different from the last, but have faith TW's, it IS possible to eliminate the vibes. Start with accurate measurements.


Also, measure as best you can, make your changes, then drive for a week. Measure again, change, drive another week. Repeat. Each change takes a few days to settle in, in my experience. Also not a bad idea to re-check your torques anyway.

 

Once again I'm amazed by your generosity in helping me. I JUST got home from Harbor Freight with the centech gauge. i'm gonna go out right now and take some measurements. I'll post my results in a few.

 

Zero'd out the gauge at (A)

(A) = 0 degrees
(B) = 5.2 degrees
(C) = 4.4 degrees
(D) = 2 degrees

Also if I zero the gauge at (B), then (C) = 1.2
If (B) = 0, then (C) = 1.2
Which is accurate from the first measurement (B)-(C)=1.2

So correct me if I'm wrong but my first step looks like i need 2 degree shims to get (D) to 0 and then i match (B) to (C) by dropping or raising the carrier bearing.

(A) needs to match (D) right? So if after I add 2 degree shims at the axle, and if i zero the gauge at (A) then (D) should equal zero right?

I think i'm learning algebra and geometry at the same time...

 

Also keep in mind that I have a prerunner. So when I measure what would be my equivelant of a tc I'm measuring like this:

 

I filled in the blanks...

 

VERY well thought out post. Great job!!

A little additional info that hopefully will assist in fixing and understanding this problem:

Why a 2-piece driveshaft in the first place? If you look from the side of your truck and observe ground clearance under the frame, you will notice that a 2-piece driveshaft will allow a better clearance for obstacles. A 1-piece shaft would be straight from the transfer case to the rear differential. When the suspension flexes, (i.e. axle drops) then the driveshaft becomes more exposed, and is at greater risk of being struck. I am not saying this is a perfect system, or that the clearance distance is some huge number, but if you put 2 identical Tacoma trucks side by side, one with a 2 piece and the other with a 1 piece shaft, then lift the frame up until the axle is at full drop, you WILL see a difference in clearance.

When trying to find different sized shims for the carrier, look at alignment shims. (Gotta go old-school a bit) Alignment shims come in different thicknesses, from 1/64" up to 1/8". Also, since they are slotted, you dont have to totally remove the bolt. Just loosen the bolt, insert desired shim(s) and tighten.

 

One more interesting thing i found. According to my diagram, you were measuring (D) with (C) set at zero in your first post. I first measured (D) with (A) set at zero.

BOTH are 2 degrees here.

Since (D) is less than 3 degrees, i'm gonna move the CB until (C) and (B) are almost equal.

 

Well, with a hair under 1/8" worth of (2) fender washers I have my axles within a tenth of a degree of each other. I'll ride this for a few days and see how it feels.

 

Update again: I keep messing with different leaf shim / CB shim thicknesses to understand what horrible vibe effect I can cause, and to duplicate other poster's problems so I can then tweak it and fix it.

My Taco now rolls super smooth (fourth successful fix) 0mph to 95mph at:

CB angle (first shaft - second shaft) : -0.6 down
Pinion angle (output flange - pinion flange): -0.6 down

I believe the two numbers being the same are just a coincidence, so don't get caught up in that. Just realize that the second shaft drops a tad faster than the first (steeper downward angle), and that the rear pinion is a tad lower than the transfer case output shaft.

I might just leave it this way for a few months, until I get that new super long range gas tank installed from CES in Bend, Oregon, which I have prepaid and am driving up to get it installed in December, but that's a different thread....

BamaToy1997: nice, uh.... shims! Better than my washers, as I almost aced my CB retaining nut (the one welded to the frame) the other night by cross threading the bolt and starting to drive it home with my air wrench. Loosening the bolt just a tad (like my slotted leaf shims) is a way better way to go. Thanks for the tip!

 

For the record, my first post, while technically removing my vibes, was wrong from a u-joint longevity standpoint, along the lines of my back yard mechanics and college physics. Second update with second set of photos is correct, along the lines of Toyota engineers and people with more experience and smarter than I am. I also eliminated the vibes using a third, and now a fourth, method, but let’s stick with the Toy program.

BaconTaco: I think you messed the two posts together, and I can't quite agree with your math. I've created a cad diagram and converted it to a pdf form for clarification, attached. You can edit the numbers on your computer, or print and scribble, whichever you prefer. Fill in the top numbers, it will calculate the bottom numbers itself, then fill in the missing info. THANK YOU for getting me to make a form we can all use and refer to, to keep us all on the same page, literally.

From what I see, you need a 2.5deg or 3.0deg rear leaf shim, with the fat part of the shim FORWARD and the pointy end POINTING BACKWARD (opposite of what most instructions will tell you), in order to bring the front of your pinion DOWN. Pay attention to installing each shim the SAME WAY UP (look for something stamped into the metal and make sure both shims are either stamp up or stamp down). Oh yeah, don’t forget you need some burly clamps to keep your leaf packs together while you replace that leaf pin with the longer one that comes with your shim kit.

Also, the way I read your numbers, your second shaft actually drops at a shallower angle than your first shaft (opposite the slightly steeper second shaft angle in my diagram). I've found that getting the CB shims such that the two shafts are close to equal, then REMOVING a few shims / washers/ whatever, reduces those 20mph-40mph vibes to zilch. In other words, the CB wants to be physically UP from the driveshaft-perfectly-in-line position, usually by 1/8” or less does the trick.

All that said, I’m curious as all heck to find out if I'm full of shit and your few washers fix your problem! I understood that you had bought out your local hardware store of washers and hadn't found a sweet spot with CB tuning alone. Keep us posted on progress!

 

Well I used a 2 degree shim and still had vibes so I flipped the cb and that seems to be working. I'll try this out for a few days and see if its really gone. If it is still there it seems to be barely noticeable. This is so far the best results I've gotten. I'll post my measurements after a few days of driving.

 

Exactly correct! Excellent work BaconTaco. By installing the shim you oriented the pinion closer to zero or slightly downwards, and by flipping the carrier bearing you raised the CB which makes the first shaft at a shallower angle and the second shaft a steeper angle. Much improved vibration I'm sure. Drive on this for a few days then measure. Now you're getting close to those tenth of a degree changes for Ultra Smooth rides. Good job!

 

Hey TW members, anyone got a lead on a 1.5 degree leaf shim? Belltech doesn't have them, ToyTec doesn't have them, Google search has failed me. I have a complete set now from 1deg through 4deg in 0.5deg increments, except for that pesky missing 1.5deg. I spoke with my local metal fabricator down the street here and they could mill me one easy enough, but started asking all sorts of "what material" questions I didn't have answers for. "uh..... metal? would metal work? probably not bamboo, not cardboard..." They were concerned about fatigue over time and wanted to know what blend of metal, tempering, corrosion characteristics, etc etc. Me put in key, me turn key, me drive. That's the extent of my metallurgy knowledge.

 

Most of the shims are aluminum.

 

Done. Thanks a million max (you tired of that yet?). Phone call to the fab guys, new shims should be ready in a few days. Asked for not slotted but with a simple hole in the middle (easier for them to make, less labor, cheaper). Once I know the price (I own a Tacoma, I don't ask price anymore.....), I'll post here if anyone else wants a set.