Drive Shaft Vibrations Solved Step-by-Step

I know it’s old, but this is an amazing write up. I had terrible vibes after my lift went on. I read this and from day one, I dropped my bearing with a 3mm washer, just like the OP, and solved 95% of my vibes. Now I can safely drive until I can solve the rest of my issue step by step.

 

Here's the procedure I used to preemptively diagnose and correct driveline vibes. Instead of leaving it buried in my build thread, I figure it'll be more useful here. Happy to hear any feedback that the experts may have, either positive or negative. @Crom, @ovrlndkull, @MattiveAmerican, @cjsqueeky, @DaveInDenver, @ItalynStylion

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Tools needed -
- Angle finder: preferably high quality, since cheap ones will sometimes give you weird values
- Small flat piece of metal: used to lay flat against the transfer case flange and rear diff flange to ensure the angle finder is mated up properly
- Pen and paper: I recommend sketching everything up as a quick visual aid, and taking additional notes as you go

First off, determine your stock driveline angles. This will allow you to calculate baseline u-joint working angle values, which will tell you what numbers are okay and what numbers are not. Pay special attention to whether the driveline angles you measure are positive or negative (angled up or down towards the front of the truck). It doesn't matter which one you call positive or negative, so long as you stay consistent. I strongly advise taking all measurements at least 3 times so you can average out the numbers you get. Crazy-looking measurements can be due to operator or equipment error; see if they are repeatable before discarding them. Use the formulas listed below to calculate your u-joint working angles. Don't sweat the math, it's just subtraction.


From there, get your lift installed. Once you have everything torqued down and sitting pretty, measure your driveline angles again. Use the same process as you did in the previous step. The more measurements you take, the better.


Did your lift change your driveline geometry? Of course it changed the angles, but did it change the direction of the angles? This will affect what corrective measures you use, if any.


Now, compare your post-lift u-joint operating angles to your stock u-joint operating angles:
- Are any of them over 3 degrees when they weren't before? According to Spicer, that's not good.
- Is your transfer case u-joint working angle over 0.5 degrees? It probably is, and it probably was before you installed the lift. So long as it isn't too far off from stock, you should be fine.
- Are your center u-joint and rear diff u-joint working angles about the same? Not exactly the same, just within a half degree of each other or so. If not, you'll probably need to take corrective measures to prevent driveline vibrations.


No matter what the angles say, take it for a test drive before installing corrective measures. Drive it slow, drive it fast, brake hard, accelerate hard, do everything you can to induce a problem. Don't just drive around the block and call it good. Bring a friend if you can so you can get another butt dyno in the mix.

From here, you have your choice of corrective measures:
- Need to reduce the transfer case u-joint angle (delta_1 on my sketch)? Flip the carrier bearing upside down. This will also affect your center u-joint angle (could reduce, invert, or increase, depending on driveline geometry) and increase your rear diff u-joint angle.
- Need to reduce the rear diff u-joint angle (delta_3 on my sketch)? Install a carrier bearing drop. This will also increase your transfer case u-joint angle and affect your center u-joint angle (could reduce, invert, or increase, depending on driveline geometry)
- Need to reduce the rear diff u-joint angle without messing with the other angles too much? Install an axle shim.
- Can't quite get the center u-joint angle and rear diff u-joint angle to match (delta_dev > 0 on my sketch)? You can get a custom single-piece driveshaft from Tom Woods, which deletes the center u-joint entirely; this is not an option for DCLB and some re-geared trucks. You can also get a two-piece double cardan driveshaft from a variety of shops, some of which may be local to you; this type of driveshaft will theoretically allow your center u-joint angle to be double the rear diff u-joint angle, which means you'll still likely need axle shims. Below is the price quote I received from a highly-regarded local driveline shop for retrofitting my OEM two-piece driveshaft with a double cardan joint and replacing all other u-joints plus the carrier bearing.


Did you buy a CB drop kit or axle shims in advance, only to end up not needing them immediately? Good on you for being proactive. I advise holding onto them until the suspension fully breaks in, just in case vibration issues manifest as the driveshaft settles into its final geometry.

 

Alright folks. So I messed with my DS angles this morning and still have vibes from 35-40mph. I even put the stock wheels/tires on and it still vibes.

Here is what I got after installing 3mm spacers to drop the CB. All the angles seem to be right where they should be, based on my extensive research. Should I try some shims in the rear?

 

@nparent2147, you want theta_2 (center u-joint operating angle) and theta_3 (rear u-joint operating angle) to match as close as possible. It looks like some 3 degree shims would get you squared away. If those axle shims overcorrect the angles, you can remove the CB shims to get the working angles closer.

@EatSleepTacos, see above. The theta is spreading.

 

Hmmm.. yea makes sense. I'm going to remove the spacer and remeasure, spacer never made a difference anyway. Then I might be able to use a lesser degree shim. Thanks!

 

With your driveshaft as-is, your center and rear u-joints are 3.1 degrees off. A 3 degree axle shim *should* get you exactly where you need to be.

That said, your front u-joint is slightly out of spec, so removing the CB shims would help there.

 

Removing the CB shim still results in the center and rear working angles to be 3 degrees off. I'll go with a 3 degree shim and see what happens.

 

Got all that @DriveShaft AngleArtist

 

dude, no. looks complicated.

I’m gonna put on my leafs and YOLO

 

May the theta be with you.

 

I never measured my stock angles, so there is that too...

 

The stock angle values are helpful, but you can probably fudge it without them. Just get everything as close to specs as you can.

 

I failed there too! Just went with what it was thereafter and ordered shim kit accordingly.

Fitting that I've got the truck sitting in the garage about to remeasure my working angles due to post tire rotation vibes in the wheel between 48-69mph.

Firestone alignment is next if the angles are still "happy".

 

Following. Just installed some deaver expo stage 2s and got some vibes on my test drive through the neighborhood.

 

@ardrummer292 thanks for the summary a few post back. This is inline with what the OP and others figured out along the way. I just read through this thread and ordered the wixey digital angle gauge. A lot of useful information. I didn't get to measure my angles before my lift but with the information I have now I should he able to figure it out.

This forum is f'ing awesome!

 

Glad I could help. No one has chimed in telling me my methodology is flawed, so I assume you won't have any issues.

 

I wonder what happen to the OP? Seems he hasn't been on here for a while. After reading through the thread, I realized he became a driveline whisperer. He took input from others like badger, Maxamillion and his own trial and error and created a process to solve the vibes. His dedication to the topic was admirable. He seemed like a legit dude too. Always willing to help others solve their vibe issues.

Why is his .pdf not a sticky in the suspension section?

 

Im going to order and install a 3degree axle shim. I currectly have a 2" add a leaf with the factory overload left in. Will i need extended u bolts? I have about an inch of thread left on the u bolts.

 

No, those shims are <1"