*UPDATE* - It's Definitely a Drive Shaft Vibration...

I crawled under the truck last night to measure my drive line angles and I confirmed I do not have OEM shims installed.

As for my drive shaft angles, I wanted to include a quote from another member about how to properly align your drive shaft in order to minimize or eliminate vibrations that has appeared in more than one thread about drive line vibrations:

From what I can tell, this particular member isn't active on the forum any more but his advice seems to be solid based on the comments other members have posted in those other threads. From what I could gather, method number one typically works the best for eliminating drive line vibrations. With that said, here are the measurements I got last night:

TC Output: 0.0° (I calibrated my angle finder on this angle)
First Shaft Angle: 5.5° down
Second Shaft Angle: 5.2° down
Pinion Angle: 3° down

Using the logic posted by badger years ago, it appears that I will need to purchase and install a pair of 3° axle shims in order to align the TC Output Shaft and the Pinion Shaft in parallel. Once that is complete I will need to remeasure my two drive shaft angles and adjust the carrier bearing as needed in order to keep the two shafts in a straight line (within less than 1° of each other). I'm going to order the axle shims right now as well as a CB drop kit (just in case) and I will report back once I have the axle shims installed and have my new measurements.

 

Axle shims and CB drop kit will be here tomorrow. Unfortunately I'm stuck in all day meetings at work the next few days and won't have the time to mess with the truck. I'm hoping to install the axle shims on Friday and I'll report back with my findings. Stay tuned...

 

Wish you luck! Subbed for update.

 

watching this thread closely. I have 5100's with 887's and 1/4" drivers side spacer, and OME Dakars and 5100's out back. I had a crappy Pro-Comp lift before and had the same takeoff only shudder, I attributed it to the blocks and round U bolts some bonehead before me put on the truck. Installed the whole new lift, Dakars, CB shims, and the shudder is still there! Lets see if your pinion shims do it. Good Luck!

 

Maybe check the differential fluid? Since you have a Sport model you have the LSD. After some time, the friction modifier in the diff fluid wears off and causes a shudder.

 

He has an 09

 

Care to elaborate for us less educated? I've always been curious if I had an LSD or not. I was under the impression I did not.

 

You do, but as i understand it 09+ have an electronic lsd that works by using the brakes. Sort of like a traction control but a little different. You dont have any mechanical cluctch pack in your rear diff like the earlier ones. But thats from what I remember, i could be wrong about the year range.

 

Someone more in the know might be able to confirm or dispute that.

 

i have a question for the pros

I flipped the CB, less vibes but still has a bit of vibe from 0-20mph .... aside from this it runs smooth.
Can flipping the CB cause u joint damage?
If I reverse the CB and just place a cb drop kit, it vibrates 0-20mph and 20-0 mph, but is it safer for the u joints?

what is best solution for a complete vibe free drive line? does it need a shim under rear leaf springs?

 

While I can't answer your reliability question, my update is very similar to your experience...

After a lot of research and deliberation, I decided against installing the 3° axle shims and instead decided to experiment with different CB locations. The first thing I tried was rotating the CB 180° and taking the truck for a drive. This resulted in a very similar experience to the stock CB orientation, I still experienced a vibration at slow takeoffs with no other major vibrations. The flipped CB did seem to be better than the stock orientation but since I could still feel a vibration at takeoff I continued experimenting. Next I installed the CB drop kit with the CB flipped. This did not change the takeoff vibration and made the low speed vibrations I would occasionally experience much more pronounced. I then decided to flip the CB back to stock and install the CB drop kit. This resulted in the best experience thus far. The vibration at takeoff is about 50% what it was stock and I don't notice any other vibrations at any other speeds.

Based on my findings and the learnings in the other threads, I'm going to stick with the stock CB orientation and continue to experiment with dropping the CB. I'm going to the hardware store tonight to pickup longer bolts so I can add a washer or two in addition to the 8mm CB drop kit. I have a feeling if I keep dropping the CB one washer width at a time I'll eventually find a position that will all but eliminate the vibrations. I'll post another update once I'm able to add a little more drop. For now, I'm hopeful that I can kick this startup vibration and enjoy my lifted truck!

 

Or, you could measure the driveline angles and make an informed decision. Every truck is different but when I installed Dakars, a 3/4" CB drop got all my angles dialed in and vibe-free.

Do note that if you lower the CB too far you will exceed the recommended "true angle" of 1-1.5 degrees. In practice however you can go a bit higher.

 

I've been measuring my angles the entire time (my original post lift angles are listed in one of my responses above). From my research I've realized that there are multiple schools of thought when it comes to lining up the angles and what's acceptable and what isn't. For me, after learning the cons of axle shims, I decided against using them to rotate my pinion angle if I could get away with it. Right now I'm at 5/16" (8mm) of drop on the CB and I'm already experiencing less vibrations. I won't take it any further than 3/4" in my attempt to eliminate all of them. If increasing the CB drop doesn't fix my takeoff vibes I'll likely just suck it up spring for a custom one piece double cardon drive shaft.

 

i did all those configurations in the past, with similar results, I did try stock CB (not flipped) with different spacers , maybe i need to keep adding spacers, i went close to 3/4" and it was still vibrating 0-20 and 20-0mph

when i flipped the CB 180 degrees, 20-0mph vibe disappeared, but 0-20mph is still there

 

i made another spacer, placed a total of 3/4" spacer and it seems to the best i have felt, just a small vibe from 30-20mph slowing down to a stop

 

OP : let us know how much spacer you ended up using, and if your vibrations went away completely... thanks

 

A few on here have had problems with the traction bars that bolt onto the 3rd member. I think it was @SMKYTXN who said the traction bar was limiting his travel. A couple others had the traction bar shear their bolts that mount the 3rd to the axle housing - creating a whole new adventure.

I hope you find the source and get it solved soon!

 

I had the ATO traction bar. I did end up shearing a few studs off the third and even twisted the mount on the third. If you're doing light wheeling the bud built and ATO bars will work just fine. I was running the ATO with Dakars and OME shocks and it obviously limited travel.

 

And there's not a whole lot of travel to limit with that setup, relatively speaking.

 

Correct.